THE SINGING SANDS

Scanned from Tales of Travel, by Lord Curzon of Kedleston (first printed in 1923)

And even things without life giving sound, whether pipe or harp, except they give a distinction in the sounds, how shall it be known what is piped or harped ? 1 Cor. xiv. 7.

Felix qui potuit rerum cognoscere causas. VIRGIL, Georgic ii. 490.

In "The Voice of Memnon " I alluded to the phenomenon known in different places and parts of the world as the Singing Sands, Sounding Sands, Rumbling Sands, Musical Sands, Barking Sands, Moving Sands, i.e. cases in which certain sands, either when set in motion, or even in some cases when apparently quiescent, give forth sounds as of music which are sometimes audible at a great distance. In former days these tales, when they appeared in the pages of mediaeval travellers, were attributed to local superstition or to an excited imagination, and were not supposed to have any scientific basis. In the course of my travels I have made a study of these cases, about which I have found a good deal not only of literary inexactitude, but of scientific uncertainty, to prevail; and as the records of the phenomena in question are widely scattered and accessible to but few, and as no attempt, so far as I know, has ever been made to collect and correlate them all, or to arrive at a definite classification, it may be worth while to set down the results of my own researches. The subject is one which, while severely scientific in one aspect, is in another full of a strange romance, since the voice of the desert, speaking in notes now as of harp strings, anon as of trumpets and drums, and echoing down the ages, is invested with a mystic fascination to which none can turn a deaf car.

There has been a general inclination to confuse with each other all cases of Musical Sands, and to assume that they are produced by similar causes or can be covered by a single definition. The very reverse is the fact ; for although a certain acoustic property is common to all these cases, it is of so varying a character, is created in circumstances so widely different, and is attributable to such divergent causes, that no one generalisation admits of being applied. I shall distinguish quite definitely between the Singing Sand-hills or slopes or dunes, and the Sand Beaches that also produce musical sounds. The former are mainly to be found in Asia, though examples have been reported in Africa and America also. The latter are much more widely diffused. It is about the Singing Hills of Asia that the atmosphere of mystery principally clings, and here I shall let each of the few travellers who have heard the music speak in his own words, so that we may compare their evidence before we attempt to form a conclusion.

1. MUSICAL SAND-HILLS

The Sounding Sands of Tunyang

If the sands of the desert speak, it were strange indeed were their voice not heard in the illimitable solitudes of Central Asia, where pilgrims for centuries have wended their patient way across the wastes, amid every variety of formation that sand, under the influence of wind or climate, could assume. It is with no surprise, therefore, that we find the doyen of mediaeval travellers, Marco Polo - who saw so much and heard so much more, and who recorded both - when he crossed the Great Gobi Desert, thus narrating his experience:

"Sometimes you shall hear the sound of musical instruments and still more commonly the sound of drums." Yule's Marco Polo, vol. ii. p. 203. London, 1874.

He does not actually say whether he heard the desert music. But the inference is reasonable; and if, as also seems probable, he is referring to a particular spot, then it can hardly be other than the celebrated Sounding Sand-hill near the Caves of the Thousand Buddhas in Tunyang.

This phenomenon is the subject of frequent mention in the works of early Chinese writers, where it is commonly called Ming-sha-shan, or the Rumbling Sand-hill. For instance, in the Tan Huang Lu, one of the Chinese MSS. brought back by Sir Aurel Stein from Tunyang, and dating from the ninth century A.D., we find the following passage :

"The Hill of Sounding Sand is 10 li away from the city. It stretches 80 li cast and west, and 40 li north and south, and it reaches a height of 500 feet in places. The whole mass is made up entirely of pure sand. This hill has strange supernatural qualities. Its peaks taper up to a point, and between them there is a mysterious hole which the sand has not been able to cover up. In the height of summer the sand gives out sounds of itself, and if trodden by men or horses the noise is heard many tens of Ii away. It is customary on the tuan-wu day (the Dragon festival on the fifth of the fifth moon) for men and women from the city to clamber up to some of the highest points and rush down again in a body, which causes the sand to give forth a loud rumbling sound like thunder. Yet when you come to look at it the next morning the hill is found to be just as steep as before. The ancients called this hill the Sounding Sand; they deified the sand and worshipped it there." Journal of the Royal Asiatic Society, pp. 48-44, January 1915. Vide also Bretschneider's Mediaeval Researches, vol. ii. p. 216 ; Remusat, Ville de Khotan, p. 77; and Palladius, Journal of the North China Branch of the Royal Asiatic Society, N.S., vol. x. p. 5 (1875).

Similar references are to be found in the Wu Tai Shih, where the hill is described as "emitting, summer and winter, a rumbling noise like thunder," and in another Chinese record, which says that "when the weather is bright and sunny the sand emits sounds which are heard in the city."

When Sir Aurel Stein himself visited this locality in 1907 he thus described the phenomenon, situated on the shores of the Crescent Lake, quite close to the caves :

"The southern shore of the lake was occupied by a number of picturesque Moslem temples rising on terraces from the water's edge and decorated with a queer medley of Buddhist and Taoist statues and frescoes. Just in front of them and across the lake rose the famous Resounding Sand-hill, often mentioned in old Chinese records. . . . I had ridden out to this secluded spot to enjoy undisturbed work. . . . But Chiang, my only companion, though he had brought out work too, could not forego the temptation of climbing to the top of the huge dune in his dainty velvet boots, just to make the sand slide down from there and hear the " miraculous rumbling " it produced. . . . We all duly heard the faint sound like that of distant carts rumbling, and Chiang felt elated and put it down in his journal." Ruins of Desert Cathay, by M. Aurel Stein, vol. ii. p. 161. London, 1912.

The sound, it will be noted, is here likened not so much to that of any musical instrument as to a distant rumbling noise, arising clearly from the displacement of the particles or grains of sand.

Reg-i-Ruwan, or the Moving Sands of Kabul

In the generation immediately succeeding Marco Polo, i.e. in the early fourteenth century, another European traveller, the inimitable Friar Odoric, of Pordenone in Italy, also made his way across the Asiatic Continent and also heard the Singing Sands. His description is more precise :

"Another great and terrible thing I saw; for as I went through a certain valley which lieth by the River of Delights, I saw therein many dead corpses lying. And I heard also therein sundry kinds of music but chiefly nakers, < ie, naqaras or drums> which were marvellously played upon. And so great was the noise thereof that very great fear came upon me. Now this valley is seven or eight miles long; and if any unbeliever enter therein he quitteth it never again, but perisheth incontinently. Yet I hesitated not to go in that I might see once for all what the matter was. And when I had gone in I saw, as I have said, such numbers of corpses as no one without seeing it could deem credible. And at one side of the valley, in the very rock, I beheld as it were the face of a man, very great and terrible, so very terrible indeed that for my exceeding great fear my spirit seemed to die in me. . . . And so I came at length to the other end of the valley, and there I ascended a hill of sand and looked around me. But nothing could I descry, only I still heard those nakers to play, which were played so marvellously." Cathay and the Way Thither (Hakluyt Society), vol. ii. pp. 262-5.

Making every allowance for the superstitious inaccuracies of the Friar, there can, I think, be no doubt that the great image by which he was so terrified was one of the colossal rock idols of Bamian, hewn in the walls of a gorge in the main Hindu Kush range, to the north-west of Kabul - they are images of Buddha - and that the hill of sand which gave forth the music of drums was the Reg-i-Ruwan or Moving Sand, some forty miles to the north of that city, on the slope of the Paghman range. The corpses which he saw were doubtless those of the hapless travellers who had been robbed and slain by the bandits who infested that region. This is the first definite reference by a European traveller to the Afghan Singing Sands. It is true that the Reg-i-Ruwan is not so near to the Bamian Gorge as the words would seem to imply ; but in the case of a traveller coming to Kabul from the North or from Afghan Turkestan, the direction and order are correctly given.

The Emperor Baber, who rode, and drank, and hunted in the neighbourhood of his capital, Kabul, and who had an eye for every wonder or beauty of nature, was not likely to be unaware of so strange a scene. He was more than once at Reg-i-Ruwan, where indeed he spent Christmas Day, 1519. He apparently did not hear the music, perhaps because he was not there at the right season of the year, but he repeated the popular belief :

"Between these plains is a small hill in which there is a line of sandy ground, reaching from the top to the bottom of the hill. They called it Khwajeh-reg-rewan. They say that in the summer season the sound of drums and nagarets issues from this sand." Memoirs of Baber, p. 146, translated by J. Leyden and W. Erskine. London, 1887. The original Turki has duhul, i.e. drum, and naqara, i.e. kettledrum.

Then ensues a long gap in our records until, in the second quarter of the nineteenth century, the political and commercial interests of the Government of India were responsible for the appearance at Kabul of a number of British officers or travellers, who were allowed by Dost Mohammed a freedom of movement about his country which nearly a century later is still denied to the foreigner. The most famous of these men was Captain, afterwards Sir Alexander Burnes, destined to be murdered at Kabul only a few years later. Among the others who were there at the same time were G. T. Vigne, the traveller, Charles Masson, the correspondent of the East India Company, Lieutenant John Wood, the explorer of the sources of the Oxus, and Dr. P. B. Lord, the companion of the latter in his journey.

The first of these in point of time to refer to the Reg-i-Ruwan was G. T. Vigne, who with Masson was in the neighbourhood of the spot in August I836, though I think it is quite clear from their joint descriptions that they did not actually visit the sand-hill or test the sound, much less hear the music.

Vigne wrote as follows:

"On a detached and comparatively low hill a whitish streak is observed, extending from the summit to the foot of it. This is the Reg-Ruwan, or Running Sand, mentioned by Baber. The natives say that it runs up again, and that it is never diminished; and that there is a cave at its foot, where noises are heard, and into which the sand falls and disappears. It may be partly owing to the decomposition of granite or other rocks, or to the peculiar shape or situation of the hill, which collects there the particles of sand, taken up by the mountain gusts, or perhaps to both these reasons, or neither." Personal Narrative of a Visit to Ghuzni, Kabul and Afghanistan, p. 219. London, 1840.

It will be observed that in the above passage Vigne is much more concerned with the phenomenon of the perpetual re-creation of the sandhill in this isolated spot than with the noise, which indeed he does not directly connect with the movement of the sand. His companion Masson similarly connects the sound with the cave and with the Mohammedan superstitions about the latter:

"At the hill of Regh Rawan, remarkable for the bed of sand lying upon its southern face, which gives it both its name and singular appearance, is a subterranean cave which has a descent by hewn and artificial stairs, and may therefore be supposed to mean something more than the ordinary rock cave. It has never been duly explored, and there might be danger in the attempt to descend into it. The Mahommedans have made it a ziarat, and have an idea that it is the spot where their expected Imam Medi will issue upon earth; and they believe that on Roz Juma, or Sacred Friday, the sound of nagaras or drums may be heard in it." Narrative of Journeys in Afghanistan, etc., vol. iii. p. 167. London, 1844.

The local belief about the Mahdi would appear to have either started from or to have given rise to another incident which is thus reported by Vigne (p. 223):

"Some years ago a fanatic from the Kohistan took up his abode in a cave near, I believe, the Reg-Ruwan, and said that he was Imaum Mihedi, who is expected by the Mussulmen to appear at the end of the world. He collected upwards of 20,000 men, many of whom dressed themselves as birds and beasts, and marched towards Kabul. They were met and defeated by the troops of the Vizier Futteh Khan."

Much more exact is the description given by Burnes himself, accompanied by a rough lithographic illustration, which depicts his native escort scrambling up the face of the sand-hill in order to evoke the music :

"The description of Baber, though it appears marvellous, is accurate. Reg-Ruwan is about 40 miles north of Cabul towards Hindu Kosh, and near the base of the mountains. Two ridges of hills, detached from the rest, run in and meet each other ; at the apex of this a sheet of sand, as pure as that on the seashore, with a slope of about 40', forms the face of a hill to its summit, which is about 400 feet high. When this sand is set in motion by a body of people, who slide down it, a sound is emitted. On the first trial we distinctly heard two loud, hollow sounds such as would be given by a large drum. On two subsequent attempts we heard nothing, so that perhaps the sand requires to be for a time settled before the curiosity is displayed. There is an echo in this place, and the inhabitants have a belief that the sounds are only heard on Friday, when the Saint of Reg-Ruwan, who is interred hard by, permits ! The locality of the sand is remarkable, there being none other in the neighbourhood. Reg-Ruwan faces the south, but the wind of Purwan (bad-i-Purwan) blows from the north for the greater part of the year, and has probably deposited it by an eddy. Such is the violence of this wind that all the trees in the neighbourhood bend to the south, and a field, after a few years, requires to be reeleared of the pebbles and stones which the loss of soil lays bare. The mountains here are generally composed of granite or mica, but at Reg-Ruwan we had sandstone, lime, slate and quartz. . . . Reg-Ruwan is seen from a great distance, and the situation of the sand is so curious that it might almost be imagined the hill had been cut in two, and that it had gushed forth as from a sand-bag, though the wind could not have brought it together." Journal of the Asiatic Society of Bengal, April 1838, pp. 324-5.

Lieutenant John Wood's account closely follows that of Burnes, and he and his companion, Dr. P. B. Lord, appear to have visited the spot in the same month (October 1837), though not, it would seem, as members of the same party as Burnes. We read in Wood's book:

"At the upper end of Koh Daman, on its eastern side, the face of the hills, at one particular spot, is covered with fine sand, called Reig-Rawan, or the Moving Sand. To this the natives of the valley ascribe the utterance of strange unearthly sounds, and by their marvellous relations induced us to visit the spot. The Moving Sand rests upon a base of 100 yards wide, and stretches up the face of the rock for 250 yards, with an acclivity of about 450. At 3 P.m. the temperature of the sand on the surface was 103', while at the depth of 10 inches it was only 75'. Looking down from the top of this sandy, inclined plain, it is seen to lie in a hollow of the rock fronting west-south-west. The formation of the adjoining rocks are limestone, and a loose, conglomerate sandstone. The first is both fractured and calcined, and the same appearance is observed at other places along the side of the valley, but is always local: that bordering the Moving Sand is strictly so. From Reig-Rawan there is no other sand deposit visible, though further south, and on the east side of the valley, there are one or two smaller strips, but which are not asserted to be vocal. The west side of Koh Daman is composed of granite, and the prevailing wind is from the north, but no sand is likely to come from either of these directions. From the known propensity of the ignorant to exaggerate everything connected with supposed supernatural agency, we did not come to the place very confident believers in the current tales of Reig-Rawan. However, we did as we were directed, and sent six men to the top of the sandy strip while we took up a position in the most favourable place to hear any noise that might be emitted. The party above came trampling down, and continued their march to the foot of the inclined plain ; but without eliciting the slightest sound. This was repeated again and again, but only once with any success. The sound then heard was like that of a distant drum, mellowed by softer music. The secret of Reig-Rawan is, I should imagine, that of the Whispering Gallery. The slightest indentation in the sand is immediately filled up by the fall of the particles above. Moving waves are thus produced by the heavy tramp of a descending party ; and the rustle of the dry sand is condensed and reverberated by the circular conformation of the rocks around." Captain J. Wood, A Journey to the Source of the River Oxus, pp. 114-15. London, 1872.

Wood's companion, the Doctor, was more brief :

"On our way back through the plain of Koh-i-Daman we paid a visit to Reg-rowan (the Flowing Sand), which has long been an object of wonder and veneration to the natives. It is simply a bed of loose sand on the slope of the hill, which, if set in motion by any cause, as by the wind or a man rolling down from the top, produces lengthened sonorous vibrations not unlike those of the string of a bass viol." J.A.S.B., June 1838, p. 537.

Wood, in the passage above quoted, referred also to the gardens of Istalif - the favourite holiday haunt of the Emperor Baber, who wrote of it: " A large river runs through it, and on either side are gardens, green, gay and beautiful," and to the Panjshir River in the same neighbourhood; and I have little doubt that here or hereabouts we have the original of Odorie's " River of Delights " ; for the mountain-sides and valleys at this spot have always admittedly been the beauty spots of Afghanistan.

But to return to the Sounding Sands. Wood's explanation, as we have seen, is that the sounds were produced by the movement of particles of sand, disturbed either by the trampling of feet or by some other artificial cause, and rustling as they fell. To this I shall revert later.

When I was at Kabul in 1894 I would have sought the Amir's permission to visit the Reg-iRuwan, had it been earlier in the year. As it was, I asked him about it. He was not in the least at a loss for a reply, which was of a severely rationalistic character, and was marked by his usual contempt for the beliefs or fears of his own people. I was the first person, he said, who had ever asked him a question about the Reg-i-Ruwan, and, having made a special study of the subject, he would therefore gladly explain it to me.

"The sand had nothing to do with the sound. The people in the neighbourhood and even at Kabul all believed that the sounds were of supernatural origin, and that within an adjoining cave in the mountains horsemen were shoeing their horses and beating their drums ; and that from this recess a new prophet would presently come forth to restore the true faith throughout the world and annihilate the infidel. <This is identical with Masson's story.> But this was not at all the case, and the explanation of the sound, which he had heard himself, was quite different. There was a shelving face of rock, which was so covered with sand as to constitute a steep sand-slope. About half-way down this slope there was an orifice or cavern in the rock, running underground for a long distance. On the left side of the slope, at a little distance, were some more high rocks, in which there were similar cavities, at a place called Parwan. <Masson also mentions the caves at Purwan, vol. iii. p. 166.> It was only when the wind was blowing from the latter orifices, and impinged upon the mouth of the orifice in Reg-i-Ruwan, that then, being whirled round and round in the mouth and interior of the cave, it produced the humming sound which had been mistaken for drums and trumpets. When blowing from Parwan the wind made a whistling sound; but when it entered the hole in Reg-i-Ruwan, then it hummed. From a distance of ten miles he had first discovered this explanation with a telescope! Then he had been up to the place and had posted men to wait and see. They reported that only when the wind blew from that quarter was the sound heard, and the greater the wind the louder the sound. But if there was no wind there was no sound heard at all."

For his own part, the Amir added, so useful was the sand for building, and so useless for musical purposes, that he was now bringing it down to Kabul to make bricks and mortar.

I have had a renewed investigation made of the Reg-i-Ruwan in the present summer (I923) by the good offices of the reigning Amir of Afghanistan and the British Resident at Kabul, for the special purposes of this volume, and I add the result of the investigations of the latter (Colonel Humphrys) in his own words. He spent the day of 24th June at Reg-i-Ruwan, and took the photograph which is reproduced here, and in which the little figures at the base of the sandslope are men :

"The range in which the moving sand is situated is semicircular in shape, with a concave face towards the south, and is an outcrop of the main Hindu Kush range, with which its greatest length-about half a mile -is parallel, running roughly east to west. It lies about 40 miles due north of Kabul, and three-quarters of a mile to the north-east of the village of Khwaja Muhammad. Height of base, according to the aneroid, 4950 feet above sea-level. Average height of the reef, 600 feet above the Panjshir plain. Formation of range, limestone, combined with some volcanic rock.

The Reg-i-Ruwan lies near the western extremity of the reef, faces due south, and is protected by the western wall of the semicircle from the direct impact of the Parwan wind, which blows with terrific force in the summer months from Parwan (or Jebel-us-Siraj), situated some ten miles away, as the crow flies, to the north-west. It may be conjectured that the western extremity of the reef, although it breaks the direct impact of this wind, gives rise to an eddy which the vacuum caused by the air rising from the extremely hot sheet of sand would draw upwards and might thus carry the sand from the bottom towards the top. This, according to local gossip, is the movement by which the bulk of the sand-slope is maintained. The angle of the sand-slope was measured to be 331 degrees. Its shape is narrowest at the top, broadening towards the bottom, regularity being impaired on the eastern side of the sand-bank by an outcrop of rock which has been enlarged by an artificial platform used on the occasion of fairs. The sand does not run to the top of the reef but only about two-thirds of the height. The vertical height from the top of sand-slope to the bottom was shown by the aneroid to be 430 feet. The sand is formed of minute particles, apparently by decomposition from the surrounding rock. It is white at the top, yellow at the western side of the base, and streaked with black on the eastern side. A ber tree (Zizyphus Jujuba), plainly visible in the photograph, flourishes about halfway up the sand-slope close to the eastern edge, and another ber tree of massive proportions stands on the platform referred to above. There are some smaller sand deposits at the eastern extremity of the reef, facing north-west, and therefore meeting the full force of the wind, and on the northern face of the range to the southeast sand deposits of some considerable size could also be seen. None of these sands, however, possess the reputation of moving. There are no caves in the reef itself, but in the shrine of Muhammad Hanifi, some 500 yards from the foot of the sand-slope, is an artificial shaft which, about 15 feet below the surface, branches into two smaller tunnels, one reported by the custodian of the shrine to lead to the moving sand and the other to Ghazni! Both tunnels were obstructed by falls of earth. Access was gained to the tomb of Muhammad Hanifi by means of rough stairs cut in the clay. Length of sand-slope from top to bottom is about 800 feet, and greatest breadth 320 feet.

There was practically no wind on the 24th June when the experiments were made. Men were sent to the top of the sand-slope and descended several times at varying speeds. As the sand became dislodged by their movements, it flowed down in parallel rectangular streams: the collapsing edge gradually worked upwards, and the downward flow continued for several minutes after the sand had been disturbed. These streams developed no lateral spread beyond three feet, and emitted a rustling sound which was faintly audible up to a distance of twenty yards The sand on the surface at midday was painfully hot to the feet, even through a boot, but about six inches below the surface it was saturated with moisture. The Afghan villagers stated that no rain had fallen in the locality for two months, and it seems possible that by the end of the summer, which is practically rainless, the sand grains would become incoherent to a considerable depth, and, according to the conjectures of former observers, would then be more likely to possess a sonorous quality.

All the local people asserted that the sand produced a sound like the beating of drums (nagaras) on certain occasions. Some said that these occasions were limited to Fridays, but the majority stated that the phenomenon occurred capriciously about ten or twelve times a year without regard to the season, and frequently without the assistance of wind or other extraneous agency. They insisted that, if the sand was carried by the wind or otherwise to a distance from the slope, it invariably found its way back to Reg-i-Ruwan during the night. This was due to a special sanctity which belonged to the place. I was informed by the Governor of Kohistan, who met me on my way back to Jebel-us-Siraj, that the late Amir Habibulla was very interested in the phenomenon, and had paid seven visits to Reg-i-Ruwan, but had not been fortunate enough to hear the music."

Colonel Humphrys, it will be observed, was unsuccessful in his experiment; but he intends to pay another visit to Reg-i-Ruwan later in the summer, when the sand may be drier and the chances of success improved. I am afraid that his description completely disposes of the too fanciful explanation of my friend the Amir, for the cave, so far from being in the reef, is more than a quarter of a mile away; and the telescope of the Amir must have been a very astonishing instrument if it did not enable him to discover this fact. No European would appear to have visited Reg-i-Ruwan since 1837, but it is evident not merely that the tradition survives but that the sands still speak.

Kalah-i-Kah, Seistan

Pursuing my way westwards, the next case that I take is that of the Moving and Musical Sand-hill at Kalah-i-Kah in Afghan Seistan, which is also called Reg-i-Ruwan. This place was well known to the Arab geographers from early times. Mukadessi, at the end of the tenth century, said of it :

"If water or any small object were thrown on the sand of this hillock, a great noise was heard like a humming sound, and very terrible to listen to." Descriptio imperii Moslemici.

In the next century Biruni wrote:

"Further, there is a mountain between Herat and Sijistan, in a sandy country, somewhat distant from the road, where you hear a clear murmur and a deep sound as soon as it is defiled by human excrements or urine." Chronology of Ancient Nations, p. 235. Translation by Sachaus. London, 1879.

These rather unsavoury details of course meant no more than that the music was heard if a movement were communicated to the sandgrains by any form of human agency.

By far the fullest account of this phenomenon is, however, that which appeared in the records of Sir Frederic Goldsmid's Mission to settle the boundary between Persian and Afghan Seistan in 1870-1872. lt was in March 1872 that the Mission found itself at Kalah-i-Kah, five miles from which in the direction of the Harut Rud stands the famous ziarat or shrine of lmam Zaid. The account of this part of the Mission's work was written by Major (afterwards Sir C.) Euan Smith; but the member of the Mission who heard the music was neither the writer nor his chief, but Captain Beresford Lovett, R.E. The place and the sound are thus described:

"This ziarat, which is called the Rig-i-Rawan, or Moving Sand, is most remarkable and singular. At the extreme west of the range of hills which has been described as lying in a straight line due north of the Kala'h-i-Kah district, is a hill some 600 feet high and half a mile long. The southern face of this hill to the very summit is covered with a drift of fine and very deep sand-which has evidently been there for ages, as testified by the number of large plants growing on its surface. None of the adjacent hills have any trace whatever of sand-drift, and the surface of the surrounding desert is hard and pebbly. The westernmost portion of this elevated ground contains the ziarat, and the natives say, and with reason and truth, that at times the hill gives out a strange startling noise, which they compare to the rolling of drums. Captain Lovett, who was fortunate enough to hear it, describes its effect upon him as like the wailing of an Aolian harp, or the sound occasioned by the vibration of several telegraph wires - very fine at first, but increasing every moment in volume and intensity; and the secret strain is said sometimes to last as long as an hour at a time. The face of the hill is concave, its cavity is filled with the sand, and underneath there appears to be a hard limestone surface. It would be useless after a summary inspection to hazard an opinion as to the cause of the remarkable sounds that proceed from the hill-but it is noticeable that they may be produced by any large number of men, at the top, putting the sand in motion. It should be remarked at the same time that the noise is often heard in perfectly still weather, and when nobody is near the hill ; and it is singular also that the limit of the sand at the bottom seems never to be encroached upon by falling sand from the summit, though the face of the hill and sand-drift is very steep. On watching the sand this morning at the time he heard the sound, Captain Lovett observed that its vibrations and the movements of the pilgrims who had gone to the summit of the drift, occurred at the same moment. The natives, of course, ascribe miraculous properties to the hill. It is believed to be the grave of the Imam Zaid, the grandson of Husain, the son of Ali. Tradition says that, being pursued by his enemies, he came to this hill for refuge, was covered one night by the miraculous sand-drift, and has never been seen again. They say that the sand, thus miraculously brought by heavenly aid, could be removed by no earthly power, and that were any one impious enough to try it, the sand would return of its own accord. They believe the hill, like the ancient oracles, to give out warning when anything important is going to happen in the district. Thus, in the time when the Turkmans used to make their forays as far south as this, the hill alwa s gave warning the night before their arrival; and we are assured that the arrival of our Mission was heralded by the same sounds. The head of the district told us that the noise could be heard in still weather at a distance of ten miles; and Sayid Nur Muhammad Shah declares he heard it distinctly last night at our camp five miles off. Shia'hs and Sunnis alike, unable to contend against the evidence of their ears, come to worship at this miraculous spot, and here find a common ground on which they can meet in amity. Obese Muhammadans do not generally subject themselves to so severe a trial of faith as that of visiting this particular Ziarat-gah. It is a very steep climb for them to the commencement of the band of sand, about 200 feet broad and nearly perpendicular; and as they sink up to the thighs in this at every step, often must they regret that the Imam could not have hid himself in a more accessible spot. The tomb is situated at the top of the sand ridge, and it is in their descent that the faithful are generally rewarded for the trouble they have voluntarily undergone by hearing the miraculous noise. Sardar Ahmad Khan, all his attendants, and a great number of stalwart Afghans, went up the hill, and we observed that they were more than half-an-hour getting across the sand ; our more effeminate Tehran servants did not seem to care to make the attempt. The base of the hill is surrounded by graves of the faithful, who, it is to be hoped, are not disturbed in their last sleep by the unearthly warnings of the object of their devotion. It is probable, after all, that science could give a very simple explanation of the phenomena ; but he would be a bold man who tried to explain the same by natural causes within a hundred miles of its influence." Eastern Persia, edited by Sir F. Goldsmid, vol. i. p. 327. London, 2 vols., 1876.

Dr. H. W. Bellew, who was a member of the party, also heard the music :

"The sand fills a wide concavity on the southern slope of a bare rocky ridge detached from the Cala Koh range, and forms an isolated mass, as remarkable from its position as from the sounds it emits when set in motion. As we passed on, our late companions on the march toilfully plodded their way up the sandy slope and the summit of the hill. Their steps set the loose particles of sand in motion, and their friction by some mysterious acoustic arrangement produced a sound as of distant drums and music, which we heard distinctly at the distance of a mile. The sounds were not continuous, but were only now and again caught by the ear, and much resembled those produced by the Eolian harp or the wind playing on telegraph wires. These sounds are often emitted by the action of the wind on the surface of the sand, and at other times without any assignable cause." H. W. Bellew, From the Indus to the Tigris, p. 285. London, 1874.

Jebel Naklus, Sinai

I now come to the particular phenomenon which, owing to its greater accessibility and to the fact that it has been visited and described by a number of European travellers, has won the widest reputation, and is commonly referred to by geographers as the classical case of a musical sand-hill. This is the Jebel Nakus or Hill of the Bell or Gong, in the Peninsula of Sinai on the eastern shore of the Red Sea. <Nakus is not a " bell " in our sense of the word. It is the wooden board suspended horizontally which is struck by a hammer in Eastern monasteries to summon the monks to prayer. In the Greek monasteries, where it is still employed, it is called " semandron."> The following is, to the best of my knowledge, a complete list of those who have left descriptions of it: Dr. U. J. Seetzen, November 1810; J. Gray (of Oxford), 1818 ; H. Ehrenberg, 1823 ; Dr. Edward Ruppell, 1827; Lieutenant J. R. Wellsted, January 1830; Lieutenant Newbold, C. Shute, June 1840 ; Capt. H. C. Butler, Rev. Pierce Butler, 18--; Professor H. A. Ward, 1855; Professor E. H. Palmer, Rev. F. W. Holland, Captain Wilson, Captain Palmer, J. Wyatt, February 1869; Dr. H. C. Bolton, 1889. Dr. Seetzen, the first European traveller to arrive upon the scene, said that he found the musical mountain composed of a white friable sandstone, presenting on two of its sides sandy declivities. He watched beside it for an hour and a quarter, and then heard for the first time a low undulating sound somewhat resembling that of a humming-top, which rose and fell, and ceased and began, and then ceased again; and in an hour and three-quarters after, when in the act of climbing along the declivity, he heard the sound get louder and more prolonged. It seemed as if issuing from under his knees, beneath which the sand, disturbed by his efforts, was sliding downwards along the surface of the rock. Concluding that the sliding sand was the cause of the sounds, not an effect of the vibrations which they occasioned, he climbed to the top of one of the declivities, and, sliding down, exerted himself with hands and feet to set the sand in motion. The effect produced far exceeded his expectations : the incoherent sand rolled under and around in a vast sheet ; and so loud was the noise produced that the earth seemed to tremble beneath him to such an extent that he would certainly have been afraid if he had been ignorant of the cause.

Seetzen further compared the moving layer of sand to a great violin bow thrown into tuneful vibrations. <"Aus einen Schreiben des Dr. Seetzen," Monall. Corresp. p. 396. Gotha, October 1812.>

Our sole English visitor in the first quarter of the nineteenth century, J. Gray of University College, Oxford, described the noise of the Musical Sands, which he heard more than once, as " beginning with a low continuous murmuring sound, which seemed to rise beneath his feet, but gradually changed into pulsations as it became louder, so as to resemble the striking of a clock, and became so strong at the end of five minutes as to detach the sand. On returning to the spot next day, he heard the sound still louder than before. He could not observe any crevices by which the external air could penetrate; and as the sky was serene and the air calm, he was satisfied that the sound could not arise from this cause." Edinburgh Journal of Science, No. XI. p. 153, No. XIII. p. 51.

Ehrenberg, in 1823, also climbed the mountain, and at every step heard a small strengthening of the tone, which swelled in volume with the increase of the amount of sand in motion, and at length became as strong as the distant thunder of cannon. He explained the vastness of the final effect as due to the piling up of small effects, as in the case of an avalanche :

"The sand-bed, which is about 150 feet high and about equally broad at its base, rises at an angle of 50 degrees, and thus rests rather on itself than on the rock, which gives it but slight support. The sand is coarse-grained and composed of very clean, even-sized grains of quartz from one-sixth to one-half a line in diameter. The great heat dries the sand by day to a certain depth (whilst it is moistened throughout by dew each night) and makes it equally dry and resonant. If, then, an empty space is formed in the sand by the sinking of a man's foot into it, the whole layer situated above this point loses its support and begins slowly to move throughout its whole length. By the flowing in of the sand from the sides and the repeated tread [of the traveller] a large part of the whole sand-layer of the slope at last acquires motion, and by its friction against the motionless under-layer produces a noise, which from a humming becomes a murmur, and in the end passes into a roar, and is all the more surprising in that one sees but little of the trickling and general movement of the sand-layer. With the cessation of the disturbance the sliding also gradually subsides as soon as the gaps are again filled and the sand-columns gain a more stable basis and a state of equilibrium is reproduced."

Another German, Dr. Ruppell, who visited Jebel Nakus in 1827, and described it as a sandstone slope 200 feet high, heaped up when the north wind blows at an angle of 50 degrees, has left an account of his visit, but does not say that he heard the music, though he adds that it is when the west wind blows that it is audible. <Der Tonende Berg Nakus in Peisen nach Nubien. Frankfurt, 1829.>

The first full description from an English source is, however, that of Lieutenant J. R. Wellsted, of the Indian Navy, who was despatched by the Bombay Government in 1829 in the ship Palinurus to conduct a survey of the Red Sea. He and his companions several times visited Jebel Nakus, and he thus recorded his experience in January 1830, together with a lithographic illustration, which a later American visitor regarded as somewhat deficient in accuracy:

"Considerable attention has also of late years been directed towards the phenomenon connected with this remarkable spot, though the accounts hitherto furnished by travellers are neither so full nor so satisfactory as could be wished. It forms one of a ridge of low calcareous hills, at a distance of 31 miles from the beach, to which a sandy plain, extending with a gentle rise to their base, connects them. Its height, about 400 feet, as well as the material of which it is composed-a light-coloured friable sandstone-is about the same as the rest of the chain ; but an inclined plane of almost impalpable sand rises at an angle of 40 degrees with the horizon, and is bounded by a semicircle of rocks presenting broken, abrupt and pinnacled forms, and extending to the base of this remarkable hill. Although their shape and arrangement in some respects may be said to resemble a whispering gallery, yet I determined by experiment that their irregular surface renders them but ill adapted for the production of an echo. Seated on a rock at the base of the sloping eminence, I directed one of the Bedowins to ascend, and it was not until he had reached some distance that I perceived the sand in motion, rolling down the hill to the depth of a foot. It did not, however, descend in one continued stream, but, as the Arab scrambled upwards, it spread out laterally and upwards until a considerable portion of the surface was in motion. At their commencement the sounds might be compared to the faint strains of an AEolian harp when its strings first catch the breeze: as the sand became more violently agitated, by the increased velocity of the descent, the noise more nearly resembled that produced by drawing the moistened fingers over glass. As it reached the base the reverberations attained the loudness of distant thunder, causing the rock on which we were seated to vibrate; and our camels, animals not easily frightened, became so alarmed, that it was with difficulty their drivers could retain them.

It is particularly worthy of remark that the noise did not issue from every part of the hill alike, the loudest being produced by disturbing the sand on the northern side about twenty feet from the base and about ten from the rocks which bound it in that direction. The sounds sometimes fell quicker on the ear, at other times were more prolonged; but this swelling or sinking appeared to depend upon the Arab's increasing or retarding the velocity of his descent. On a spot so desert and solitary they have an inconceivably melancholy effect, and the Bedowins trace them to several wild and fanciful causes: the tradition given by Burckhardt, that the bells belonging to the convent have been buried here, has often been repeated to me.

When I visited the Jebel Narkous on two other occasions the results were much less satisfactory. The first time the sounds were barely audible, and, rain having fallen a short time previous to my second visit, the surface of the sand was so consolidated by the moisture that they could not be produced at all. I therefore attribute the complete gratification of my curiosity in this instance to the sand being perfectly dry, and consequently larger quantities rolling down the hill. That the explanation of this phenomenon is intimately connected with the agitation thus produced can admit of no doubt ; but the precise causes which lead to these results it seems difficult to explain. It may be broadly stated that the particles of sand, when in motion, roll over a harder bed, and meet in their progress the wind then blowing directly on the face of the hill at a certain angle. I should mention that the same sounds are produced when the wind is sufficiently high to set the sand in motion ; but I reject, without hesitation, the generally received opinion that the effects I have described are originated by this sand falling into cavities. Sounds thus produced would be dull and wholly deficient in the vibrations which I have noticed." <Travels in Arabia, vol. ii. pp. 23-27. London, 1838.>

Ten years later, another British officer, Lieutenant Newbold, of the Madras Army, appeared upon the scene, and gave an even more ample account of his successful experience :

"Ten minutes' walk over sand and stones brought us to the base of Gebel Nakus. The apparent height is from 350 to 400 feet. On the western side, which faces towards the Red Sea, is a steep slope of a triangular form extending about 80 feet up the side of the hill, narrow at the top, but widening out as it approaches the bottom. This slope is bounded by low cliffs of sandstone on all sides except the base, and covered with a very fine quartzy sand of a light reddish-brown colour. The sand varies in depth from a few inches to five or six feet, according to the irregularity of the sandstone rocks which lie beneath it. It has evidently been conveyed to its present position, on the slope of the rock, by the strong prevailing westerly winds. Our Bedouin guide instantly pointed to this sandy slope as the spot whence issue forth those mysterious Memnonian sounds, to which the mountain owes its appellation, and which the superstitious Arabs, as noticed by Burckhardt, believe to be produced by the bells of a subterraneous convent.

We strained our ears to catch a sound, but in vain a deep silence, hardly broken by the faint murmurings of the wind, reigned over the singularly dreary and arid wastes around. The Bedouin, having desired us to wait at a rock at the foot of the slope, commenced its ascent, sinking knee-deep in the loose sand that covered it. Presently we heard a faint musical sound resembling the deeper chords of a violoncello at a distance, prolonged, and lightly touched. The Bedouin now descended; and, on my expressing some disappointment at the result, remarked with much phlegm, that the day was not propitious; but that, if we would come on the Juma, or Muhammedan Sabbath, we should hear the mountain strains to much greater advantage. My friend, Mr. Shute, of the Inniskillings, and myself, having now obtained some clue to the cause of the sounds, determined to put the guide's veracity to the test, and accordingly commenced the ascent, which we found fatiguing, from the depth and extreme fineness of the sand, and from the intense heat of the sun. Having reached the top, I seated myself at the base of the mural cliffs which crest the summit, and watched the course of the sand we had set in motion, as it passed downwards in undulating and gradually widening lines to the base. The particles of sand displaced in the lower part of the slope disturbed those immediately above and below them; and, more slightly, those on their sides ; so that the disturbance of the upper layers of sand went on increasing on every side, somewhat resembling the effect produced on the surface of still water by dropping a stone into it.

About two minutes after the sand had been first set in motion, a faint rustling sound, as it rolled down, struck our cars : then the low, deep, distant, musical tone we had first heard, which generally became more and more distinct, and apparently nearer, in successive and fast repeated notes, whose sound partook of those of a deep mellow church or convent bell, and of the vibrations of a stringed instrument. On again disturbing the sand near the summit with my feet, the sounds took up a more treble and prolonged tone, resembling the wild strains of an Eolian harp, but gradually becoming deeper and louder, until at length they rivalled the continued rumbling of distant thunder, and fairly caused the sand on which I sat to tremble in distinct vibrations. This intensity of sound was produced a short interval after the whole surface of the sand had been set in motion from the summit to the base. The sensations imparted by the vibrations were most extraordinary; I can only compare them with those likely to be experienced by a person seated on the body of some enormous stringed instrument while a bow is slowly drawn over its chords. The greatest effect was produced by traversing the sand from right to left, and vice verso.

I descended to the base during the greatest intensity of the sounds, and awaited in silence their cessation, which took place with that of the motion of the sand, at the expiration of about a quarter of an hour.

Travellers have frequently attempted the explanation of this curious phenomenon. Some are of opinion that the sounds are caused by the sand's motion over hollow rocks; others imagine them to proceed from the sand falling into cavities; some, again, suppose them to have their origin in subterranean volcanoes ; and a few have thought that similar sounds may be produced by the action of the wind on the thin elastic plates of mica which abound in granite and gneiss. The notion of the Arabs, that the sounds are those of the bells of a subterraneous convent, has doubtless been derived from the idle tales of the monks of Mount Sinai, who declared to me that they had never been heard until after the destruction of one of their convents near Tor, and the death of the Forty Martyrs.

With regard to the first and third of these opinions, I can only observe that, on a careful examination of the rocks over which the sand rolled, they proved to be of a massive whitish sandstone or grit, of a granular texture, imbedding pebbles of quartz, and entirely free from caverns, or holes of any magnitude. No volcanic rocks, nor traces of extinct volcanoes, were found in the vicinity. Erratic fragments of porphyry, granite, greenstone and melaphyre, evidently transported from the lofty ranges of Sinai in the interior, occurred strewed on the surface of the desert not far distant. Were the sounds volcanic, they would be absolutely independent of the motion of the sand, which I shall have occasion to notice as an indispensable condition to their production. The idea of their being caused by sand falling into the cavities of the rocks appears to me to be nearly as satisfactory as the tale of the subterraneous bells. Sand in falling produces nothing beyond a dull, rustling noise, as may be readily proved by experiment. With regard to the hypothesis of wind acting on the thin and elastic plates of mica, I may remark that I could not detect a single plate of this mineral in the rocks of the locality, which were all of a sandy and calcareous character. I am not, however, prepared to deny the possibility of sounds being produced, under certain conditions, in the crevices of rocks of granite, gneiss, etc., which abound in mica.

My own ideas as to the cause of the phenomenon of the Mountain of the Bell coincide in a great measure with those of Lieutenant Wellsted, who has expressed his opinion that its explanation is intimately connected with the agitation of the sand. The inclination of the slope, down which the sand falls, is nearly that at which sand lies when poured down in a heap. It rolls down this slope, after having been disturbed, in a westerly direction; the surface of the subjacent sandstone rocks is uneven and step-like. In falling, the sand collects into waves, about an inch or two inches high, resembling those of a thick liquid flowing slowly down an inclined plane. These waves widen out as they approach the base of the slope, and acted upon by the wind, which was at the time of my visit blowing pretty strongly from the north-west, nearly at an angle of 45' with the course of the sand, form into festoon-like curves. The sounds produced on first disturbing the sand near the summit of the plane were, as before remarked, of a treble nature ; but gradually deepened, and became graver and louder, as the undulations lengthened on their way downwards to the base ; apparently on the principle of the difference of sounds produced by the strings, of different lengths, of a musical instrument.

This effect was increased by the peculiar shape of the plane down which the sand glided, which, from circumstances of its being narrow at top and broad at the base, admitted of the gradual extension or widening of the waves of sand, or, if I may so express myself, the lengthening of the strings, and the consequent deepening of the strains, of this great natural AEolian harp.

That the sounds are caused principally by the motion of the sand is further proved by the perfect stillness of the locality so long as the sand remains undisturbed ; by the gradual increase, diminution and cessation of the sounds with those of the motion of the sand, and by their being inaudible in wet weather, when the surface is consolidated, as observed by Lieutenant Wellsted. That the action and direction of the wind is a favourable, if not a necessary, condition, is proved by the sounds being faint, according to the testimony of my Bedouin, in calm weather, and sometimes inaudible; such was probably the case on the occasion of Lieutenant Wellsted's first unsuccessful visit. Further information, however, is desirable on these points ; and it would be interesting to visit the locality during the prevalence of an easterly wind. I hardly need remark that the north-west winds blow with so much violence occasionally as to disturb the sand, and thus produce the sounds without the aid of man. It would also be useful to take careful relative measurements of the locality, to ascertain the force and direction of the wind most favourable for producing the sounds, with a view of constructing a model on a small scale, from which similar effects might probably be produced artificially, and the curious question regarding the possibility of moving lines of loose sand producing, under any circumstances, musical sounds, decided beyond the shadow of a doubt. It is not a little singular that Gebel Nakus should be, as far as I am aware, the only known spot on the globe where the necessary conditions exist for producing those remarkable sounds, <He was of course mistaken.> although I have seen several localities in Arabia, Egypt and Spain where loose sand has been accumulated on the sides of rocks in an apparently similar manner. But it must be remarked at the same time that opportunity did not admit of a careful comparative examination of these localities." "Visit to Gebel Nakus, or the Mountain of the Bell, in the Peninsula of Sinai, on June 10, 1840," Journal of the Royal Asiatic Society of Great Britain and Ireland, vol. vii. p. 79, 1843.

I have not met with the account of the visit to Jebel Nakus of Professor H. A. Ward in 1855. But the well-known narrative of the expedition of Professor E. H. Palmer to determine the disputed sites of Exodus in the Desert of Sinai contains a full description of his visit to Jebel Nakus in February 1869.

"It is situated at about three-quarters of a mile from the sea-coast, and forms the north-western extremity of the range of hills which we had just crossed to our camp at Abu Suweirah. The mountain itself is composed of white friable sandstone, and filling a large gully in the side facing west-south-west, is a slope of fine drift sand about 380 feet in height, 80 yards wide at the base, and tapering towards the top, where it branches off into three or four narrow gullies. The sand lies at so high an angle to the horizon, nearly 30', and is so fine and dry as to be easily set in motion from any point in the slope, or even by scraping away a portion from its base. When this is done the sand rolls down with a sluggish viscous motion, and it is then that the sound begins, at first a low vibratory moan, but gradually swelling out into a roar like thunder, and as gradually dying away again until the sand has ceased to roll. To me the sound seemed more like that caused by air entering the mouth of a large metal vessel, and I could produce an imitation of it on a small scale by turning my flask at a certain angle to the wind. We found that the heated surface was much more sensitive to sound than the cooler layers beneath, and that those parts of the slope which had lain long undisturbed, produced a much louder and more lasting sound than those which had recently been set in motion, thus showing that the phenomenon is purely local and superficial, and due in some manner to the combined effects of heat and friction. A faint sound could also be produced by sweeping portions of the sand rapidly forward with the arm ; and this caused such a peculiar tingling sensation in the operator's arm as to suggest that some electrical influence was also at work. When a large quantity of the sand was set in motion and the sound was at its height a powerful vibration was felt, and straws stuck into the sand trembled visibly although there was not a breath of wind to disturb them. The sand on the upper part of the slope where it branches off into the gullies above mentioned is coarser and more adulterated with extraneous particles, detritus from the overhanging rocks, and pieces of seaweed blown up from the shore; it is consequently less easily set in motion, and we found it to be much less sensitive to sound. The inclination of the slope is the " angle of rest " of the sand in its normal state ; but excessive heat or drought, wind, animals running over the slope, falling rocks, and many other accidents might act as disturbing causes ; in any of these cases the sound would occur, and its spontaneous production, which has caused so much speculation, may be therefore easily accounted for. Besides the large slide there is a narrow slope to the north ; and part of this, being in shade the whole day long during the winter months, afforded us an opportunity of determining the comparative sensitiveness of the heated and cool sand. We found that the sand on the cool, shaded portion, at a temperature of 62' produced but a very faint sound when set in motion; while that on the more exposed parts, at a temperature of 103' gave forth a loud and often even startling noise. Other sand-slopes in the vicinity were also experimented upon, but these, which were composed of coarser grains and inclined at a lower angle, produced no acoustic phenomena whatever. The Arabs declare that the sounds are only heard on Fridays and Sundays, and tell the following legend respecting their origin :

An Arab whose people were encamped by the palmgrove of Abu Suweirah, happened to stroll alone by the sea-shore, and coming to the spot in question, which he had hitherto believed to be barren and uninhabited, he was surprised to find a small monastery and a pleasant garden on the mountain side. The brethren received him courteously, and invited him to partake of their meal, to which, being hungry and fatigued, he gladly consented. Having shared their hospitality, he prepared to depart, but first, at the instance of his hosts, he took a solemn oath that he would never reveal to any living soul the secret of their retreat or of his own meeting with them. He was accompanied for a portion of his way home by two of the monks, who reiterated their injunctions of secrecy and took their leave. The Arab, however, prompted either by curiosity or baser motives, took the opportunity of dropping the stones of some dates which he had eaten, in order that he might have a clue by which to find the place again ; and on reaching the tents of his tribe he at once related his adventure, regardless alike of his oath and of the sacred laws of hospitality. His people refused to - credit his account until he offered to conduct them himself to the place; but, when he attempted to do this, he found that all the date-stones had been removed. He did, however, succeed in identifying the mountain, but the monastery, gardens, and monks had all disappeared, and nothing remained to show that they had ever existed save the sound of the nagus calling them to prayers within their mysterious retreat in the very heart of the mountain. The Arab who had thus disregarded the sacred obligations of bread and salt, not only forfeited the esteem of his own people, but misfortune after misfortune overtook him until he perished miserably, an outcast from his fellowmen." The Desert of the Exodus, part I. pp. 217-221. Cambridge, 1871.

I have quoted Professor Palmer's description of Jebel Nakus at length, because, if reference to it is desired, this will be easily accessible to any reader. But a nearly identical, though more purely scientific, account was given by Captain H. S. Palmer, R.E., in the official publication, entitled Ordnance Survey of the Peninsula of Sinai, which had been brought out by H.M. Government two years earlier, in 1869. The description of the sounds, as heard by the party, is even more precise (pp. 131-134) :

"The sound is difficult to describe exactly ; it is not metallic, nor like that of a bell, nor yet that of a nagus. Perhaps the very hoarsest note of an AEolian harp, or the sound produced by rubbing the finger round the wet rim of a deep-toned finger-glass, most closely resembles it, save that there is less music in the sound of this rolling sand. It may also be likened to the noise produced by air rushing into the mouth of an empty flask or bottle; sometimes it almost approaches the roar of very distant thunder, and sometimes it resembles the deeper notes of a violoncello, or the hum of a humming-top."

Captain Palmer went on to say:

"The motion may be produced by design in various ways-by scraping away a portion at the foot of the slope; by walking directly or slantwise up it; or, which is the most effectual method, by ascending the cliffs at its side, and then scrambling rapidly along the whole face of the upper part of the slope, or slipping down and displacing the sand with one's hands and feet. The sand thus set in motion from any high point rolls slowly down over the surface in thin waves an inch or two deep, just as oil or any thick liquid might roll over an inclined sheet of glass, and in similar festoons or curves. In its passage, each wave slightly disturbs the sand below it and at its sides ; then the waves gradually spread as they descend over the constantly widening surface of the slope, and the sound soon reaches its highest pitch ; approaching the bottom the film gets thinner and thinner, at length all movement ceases, and with it the sound."

Of the various natural causes by which motion of the sand and consequent singing might be produced, Captain Palmer named the wind (the prevailing direction of which is from the northwest), intense heat, and drought. Among possible artificial causes he enumerated the movement of animals, such as gazelles, hyaenas, wolves, foxes, hares, or jerboas, crossing the slide ; or rocks rolling down from the heights above; and, of course, the accidental or deliberate actions of man.

With the Ordnance Survey was published an engraving of the sand-slope of Jebel Nakus, which is reproduced here, and which may be compared with Lieutenant Wellsted's drawing engraved in his book. <Travels in Arabia, vol. ii. p. 24.> The latter sketch represents the sand as apparently lying at a much steeper slope, and suggests exaggeration. Indeed the American, Dr. Bolton, said that it was quite inaccurate.

Such was the record of their experience and impressions left by a series of English travellers of knowledge and repute in the second and third quarters of the past century. It is remarkable to me that, Tor being a regular station for visitors to Sinai, so few, even among professional travellers who have touched or halted there, have seized the occasion to visit Jebel Nakus. Burton's ship was detained at Tor on his journey to Mecca, but he does not refer to the hill on that occasion. Nor does H. Brugsch, who spent three days in the town. <Wanderung, p. 22 et seq. Leipzig, 1866.> Elisee Reclus gives a clear local map showing the Nakus, but does not even refer to it in his text. <Geographic Universelle, vol. ix. p. 822.> No modern addition, indeed, has been made to the rather scant compendium which I have compiled until, in the eighties, a number of American scientists, who had devoted themselves with great application to the study of the problem of Musical Sands, turned their attention to Jebel Nakus, one of their number, Dr. H. C. Bolton, eventually deciding to visit the spot. The narrative of his journey in 1889 contains our latest information. In May 1889 Dr. Bolton's Report appeared in the Transactions of the New York Academy of Sciences. It will be seen that he heard the music, but in no striking degree :

"The name Jebel Nagous is given by the Bedouins to a mountain nearly three miles long and about 1200 feet high, composed of white sandstone bearing quartz pebbles and veins. On the west and north-west are several large banks of brown sand inclined at high angles. The sand on one of these slopes at the north-western end of the mountain has the property of yielding a deep resonance when it glides down the incline, either from the force of the wind or by the action of man. This bank of sand I distinguish from the others by calling it the Bell Slope. It is triangular in shape and measures 260 feet across the base, 5-8 feet across the top, and is 394 feet high. It has the inclination of 31' quite uniformly. It is bounded by vertical cliffs of sandstone and is broken towards the base by projecting rocks of the same material. The sand is yellowish in colour, very fine, and possesses at this inclination a curious mobility, which causes it to flow, when disturbed, like treacle or pitch, the depression formed being filled in from above and advancing upward at the same time. The sand has none of the characteristics of sonorous sand found on beaches. When pulled downward by the hand, or pushed by the feet, a strong vibration is felt and a low note is plainly heard, resembling the deep bass of an organ-pipe. The loudness and continuity of the note are related to the mass of sand moved, but I think that those who compare it to distant thunder exaggerate. The bordering rocky walls give a marked echo, which may have the effect of magnifying and prolonging the sounds, but which is not essential. There are no cavities for the sand to fall into, as erroneously reported. The peak of Jebel Nagous rises above the Bell Slope to the height of 955 feet above the sea-level."

In October 1889 Dr. Bolton made a further Report of the same visit, in which he described the sand of Jebel Nakus as very fine granules, yellowish white, and composed chiefly of quartz and calcareous sandstone, and added that " the sand of the slope is derived partly from disintegration of the rock itself and partly from the more distant plain below, from which violent winds blow it up on the mountain side."

Other Arabian Sands

The same thought, however, occurred to Dr. Bolton as must have presented itself to some of my readers, viz. whatever the cause or explanation of the sounds, how comes it that in countries and in regions where sand-dunes, sand-hills, and sand-drifts abound, apparently not differing widely from each other in shape or composition, the music is heard in so few places, and that Singing Sands, instead of being a normal, are so rare a phenomenon ? Accordingly he began to search in the neighbouring area for parallel sites, and without difficulty he discovered another sounding sand-hill 45 feet high, in the Wadi Werkan, five minutes off the regular caravan route to Egypt, and one and a half days by camel from Suez. The spot is called by the Bedawin Ramadan, and is thus described by Dr. Bolton. The sand, when blown by the north wind, is carried over a range of cliffs and is deposited on their south side, where it rests on the steep face at an angle of 31' at the top and 21' or less below. On being stirred by the hand, the sand yielded the bass note, already heard at Jebel Nakus, and audible 100 feet away. <Transactions of the New York Academy of Sciences, May 1889, p. 182. > Probably, if similar investigations were conducted, a good many sand-dunes, where the particular combination of conditions, essential to the production of the music, exists - what they are I will discuss later on - could be found; attention having been concentrated on a few sites where the phenomenon whether in respect of the size of the sand-hill, or of the sounds produced, is on a larger scale, or has become associated either with the burial of a saint or some local superstition.

Burckhardt, when he was in the Sinai Peninsula in May 1816, heard of Jebel Nakus, and the Bedawin tales concerning it, but made no effort to test them by visiting the spot. On the other hand he heard even more precise stories about a similar phenomenon in another mountain of the Sinai group:

"Several Bedouins had acquainted me that a thundering noise, like repeated discharges of heavy artillery, is heard at times in these mountains ; and they all affirmed that it came from Om Shomar. The monks (of the Convent of St. Catherine) corroborated the story, and even positively asserted that they had heard the sound about midday five years ago, describing it in the same manner as the Bedouins. The same noise had been heard in more remote times, and the Ikonomos, who had lived there forty years, told me that he remembered to have heard the noise at four or five separate periods. 1 inquired whether any shock of an earthquake had ever been felt on such occasions, but was answered in the negative." Travels in Syria and the Holy Land, pp. 587-591. London, 1822.

Burckhardt then made a special visit to Om Shomar, but without result.

Niebuhr, who was in the same neighbourhood in the previous century and gave an illustration of Tor, makes no reference either to Jebel Nakus or to any other Sounding Sand in the vicinity.

Another German traveller who made the journey from Cairo to Medina and Mecca in April 1845, Dr. G. A. Wallin, also refers to a place, called by his guide Wadi Hamade, somewhere in Northern Arabia north of Medina. He did not apparently either visit it or hear the music. But the Arab informed him that sometimes very strange sounds, like those of kettledrums, are heard to rise from the earth, without any one being able to account for this extraordinary phenomenon. Journal of the Royal Geographical Society, vol. xxiv., 1854.

So great a traveller and so profound a scholar as C. M. Doughty could not be expected, in his classic of Arabian travel, to leave the phenomenon of the Sounding Sands unnoticed, and accordingly we read with no surprise the following passage :

"In the Nefuz, towards El-Hyza, are certain booming sand-hills-Rowsa, Deffafiat, Subbia and lrzum, such as the sand drift of Jebel Nagus, by the sea village of Tor in Sinai; the upper sand sliding down under the foot of the passenger, there arises, of the infinite fretting grains, such a giddy loud-swelling sound as when your wetted finger is drawn about the lip of a glass of water, and like that swooning din after the chime of a great bell or cup of metal. Nagils is the name of the sounding-board in the belfry of the Greek monastery, whereupon, as the sacristan plays with his hammer, the timber yields a pleasant musical note which calls forth the formal colieros to their prayers ; another such singing sand drift, El-Howayria, is in the cliffs (east of the Mizham) of Medain Salih." Travels in Arabia Deserta (circ. 1876), vol. i. p. 307. Cambridge, 1888.

H. St. J. Philby, the most recent and adventurous of British travellers, in the Heart of Arabia, which title he has given to his excellent book (1922), tells me that he never heard the phenomenon himself, but that he was often told about it by the Arabs, more particularly in relation to the dead city of Jahura, never visited by a European, and hidden away in the Great Desert, somewhere about the 22nd parallel of latitude and the 51st of longitude, midway between the borders of Hejaz and Oman. There the sounds of drumming and moaning are regularly heard at night by passing travellers, by whom they are of course attributed to jinns or ghosts, persons of weak intellect having even been known to lose their reason. This, however, may be a case of merely imaginary haunting, the product of superstition.

Sir Richard Burton, though he does not appear anywhere to have heard the music, refers to examples in Midian. He also only quotes the evidence of others. A party from his expedition, headed by Lieutenant Amir Rushdi, were at a distance of about three hours, or eleven miles, from Sharma camp, when-

"Some pyramids of sand were pointed out in the Wady Ratiyah. The Bedawin call one of them the Goz el-Hannan (Moaning Sand-heap). They declare that when the Hajj-caravan passes, or rather used to pass, by that way, before the early sixteenth century, when Sultan Selim laid out his maritime high-road, a naubah (orchestra) was wont to sound within its bowel. This tale is told of two other places in Midian." Land of Midian, vol. i. p. 65. London, 1879.

It is true that some of these tales only repeat second-hand hearsay or even more remote tradition. But they testify to a widespread belief in the existence of a phenomenon which there is no reason to doubt, and the manifestations of which are much more calculated to surprise us by their rareness than by their frequency.

Jebel-ut-Tabul

In my studies I came across a passage in the travels of Ibn Batutah, the Moor of Tangier, who journeyed extensively in the East about A.D. 1330, and who thus described a place on the road between Medina and Mecca, which he called Jebel-ut-Tabul or the Hill of Drums.

"At Bedr there is a spring the water of which forms a canal. The site of the well in which the idolaters - enemies of God - were thrown, is now a garden, and the burial place of the martyrs is behind it. The Mountain of Pity (Jebel-ur-Rahma), where the angels descended (Koran, iii. 119-121), is on the left hand of any one who enters upon this last spot in order to proceed towards Safra. In front is the Mount of Drums. It resembles a vast hill of sand, and the inhabitants of these countries declare that every night between Thursday and Friday they hear in this place a noise as of drums. The site of the hut of the Missionary of God, in which he spent the day at Bedr, in prayer to his Lord, is at the foot of the Mount of Drums. The place of combat is opposite to it." Voyages d'lbn Batoutah (Defremery), vol. i. p. 296. Paris, 1853. <The allusion is of course to the famous battle of Bedr, in which Mohammed defeated the Meccans in A.D. 623.>

I sought for references to this spot in the published works of Burton, Burckhardt, and others who have made or described the journey from Medina to Mecca, but could not find any.

I then referred to King Hussein of the Hejaz, who replied that he knew the locality well, having built a small mosque at the foot of the hill to commemorate the famous victory of the Prophet, but that, though he was familiar with the rumour, he had never himself heard the drums. On the other hand, his son, Amir Abdullah of Transjordan, spoke of the phenomenon at Bedr as being of frequent and notorious occurrence.

He added the information, derived from his Bedawin followers. who claimed to have themselves heard the music, that sounds of thundering and groaning are also heard at night, and on most nights, in the sand-belt known as Arq-alSubai in the neighbourhood of a locality known as Abraq-al-Manazil, on the way to Taif; and also in the sands near Khanug, which is described as lying ninety-five miles E.S.E. of Medina. These assertions, if true, are peculiar in ascribing the sound to night time, when the majority of the causes that are believed to produce the sound are unlikely to be in operation. In all these cases it is difficult to distinguish experience from rumour and truth from superstition. But at least the testimony tends to corroborate the belief that the Arabian sands exhibit many instances of the phenomenon.

While I was writing this paper the representative of King Hussein, who happened to be in London and heard of my investigations, gave me the following note:

"There is a place at Beirut, called Es-Sadat, which is said to produce a musical sound. It is compared to a tambourine.

The place is a cave dug out in a rocky hill situated in the extreme western point of the city of Beirut and faces the " Pigeon Rocks " or " Shubra." The hill on the north dominates a vast sandy beach, which stretches from the foot of the hill all along the coast to a point five miles to the north-west. The sandy beach rises in some places to form a sandy hill.

The people of Beirut say that they hear the music on Friday nights, and it is attributed to the playing of the Sadat-the Masters. These apparitions gather on Friday nights in that cave and go through the thikr with tambourines in the manner of the thikr to-day, as practised in some places after prayers on Friday.

There is a man from Beirut, now in London, who says that when he was a boy he himself heard the music. His son added that his grandmother used to sit on Friday nights till late to hear the tambourines of the Sadat. They said that there are some people in Beirut who pretend to have seen people in white clothes going into the cave at night."

I accordingly asked the British Consul at Beyrout to visit the place. He found that the ground in the neighbourhood of the cave is now in the occupation of the French naval authorities, who have erected a wireless station there, and that the cave itself, which is high enough to admit of a man standing upright in it, is used by the sailors as a petrol-store. The high ground on which it is situated dominates a large expanse of sand and sand-dunes, sometimes rising to a considerable height, but lying at some distance from the cave. The French have never heard any sounds; but native witnesses who have lived in the neighbourhood for many years have heard the music emanating from the cave (though not recently) and described it as resembling the sound of a beaten tambourine. They added the not unexpected detail that the music was always heard on Thursday evenings (i.e. on the eve of the Holy Day) and was accompanied by the voices of persons invoking the names of Allah and Mohammed! There I must leave it. It is quite possible that at an earlier date before the dunes were planted, as they have been in many places with pines, and built upon, some or other of the sand slopes may have been musical, and that the sounds so heard were connected by the superstitious natives with the mystery of the cave. The conditions which produced vocality, if it ever existed, may now have ceased to operate.

Before leaving the Continent of Asia, I should add that Sir H. Yule refers to a case in the hills between the Ulba and the Irtish, in the vicinity of the Altai, which he calls the Almanac Hills, because the sounds are supposed to prognosticate weather changes. <Marco Polo, vol. i. p. 206.> But the only reference to these mountains of which I am aware is in a German publication, where they are called the Kalendar Mountains, and are said to give out a sharp report before bad weather - a phenomenon not without parallel, but bearing no relation to the Singing Sands . <Statement by Meyer in Ledebour's Reise, vol. ii. p. 186. Berlin, 1830.>

The Libyan Desert

It would be strange if no similar tales were forthcoming from the immense sand deserts of Africa, where the necessary conditions could hardly fail in some places to exist. But in the meagre literature of the subject I have found no such reference, and I only owe the two following records to my own research.

In April 1909, W. J. Harding King, travelling in the Libyan Desert, to the west of the Nile Valley, heard the song of the sands amid the dunes, some sixty feet high, not far from the Dakhla Oasis. The plateau over which he was journeying consisted of sandstone, but the meteorological conditions were somewhat unusual. After a week of great heat, followed by a cool, almost a cold day, with slight showers, a downpour of rain occurred for a quarter of an hour before sunset. Then was heard the music.

"The sound began at 7.30 P.m. and continued till about 8. It was very faint. There were two distinct sounds; the one somewhat resembled the sighing of the wind in telegraph wires, and the other was a deep throbbing sound that strongly reminded me of the after-reverberation of Big Ben. . . . It was very difficult to determine the direction from which the sound came, but apparently it came from a place about a mile distant, where the sand poured over a low scarp. The sound was a distinctly musical one, as opposed to a mere noise." Geographical Journal, vol. xxxix., 1912, pp. 133-4.

The Western Sahara

The German traveller, Dr. Oskar Lenz, who made long and adventurous explorations in the years 1874-80 in the Western Sahara, between Timbuctoo and Morocco, testifies to the same phenomenon at a spot in the Igidi region, near the well Bir-el-Abbas, a little north of 25' north latitude, longitude about 6 1/2' west of Greenwich.

"Here in this Igidi region I observed the interesting phenomenon of the Musical Sand. In the midst of the solitude one suddenly hears emerging from the interior of a sand-hill a long-drawn hollow tone, like that of a trumpet, which continues for a few seconds, then stops, only to sound again from another spot after a short interval. This makes a weird impression in the deathlike stillness of the uninhabited waste. It should be remarked at once that there is absolutely no question of an acoustic illusion, comparable to the optical illusions to which one may be subject. Not only I, but all my people, heard these hollow tones, and the guide Mohammed already called our attention to this phenomenon the day before.

The long-extended sand-dunes of the Igidi, which form regular chains of hills with sharp corners and summits, have, like all dunes, a gently rising surface directed towards the wind and in part at least a very steep fall on the opposite side. Here too they consist of a loose, very pure, light yellow quartz sand, which is heated as in a furnace by the sun. When these sandhills are crossed by a caravan a movement is set up of the lightly-piled resonant quartz grains-which movement, at first limited to a small space, draws constantly larger circles into sympathy with itself, and, like an avalanche, spreads itself over the whole surface of such a sand-hill. The motion of the loose sand-grains causes them to collide feebly with each other, by which an ever so slight note is produced ; by reason of the great volume of the moving sand-grains and the summation of the, individually, extremely feeble tones, a noise results which may attain a quite extraordinary strength. As a rule the phenomenon occurs only when the sand is set in motion artificially, by men or camels, and when the disturbance of equilibrium penetrates somewhat deeply into the mass. Camels often sink knee-deep into the loose sand. A mere superficial movement, such as may be caused by the wind, will produce the phenomenon in a very much slighter degree." Timbuktu: Reise durch Marokko, die Sahara und den Sudan, vol. ii. p. 53. Leipzig, 1884.

South Africa

I have found a single mention of a Singing Sand-dune in South Africa, on the west side of the Langberg Mountain in Western Griqualand, on dunes 500-600 feet in height. But the description of the musical sand is unfortunately omitted by the author, though apparently it had been recorded by him. Twenty-five Years in a Wagon in South Africa, by A. A. Anderson, vol. i. p. 92. London, 1887.

North America

In North America I have come across a single record of a Singing Sand-dune, analogous to the Asian and African cases which we have been discussing, and differing from the Musical Sandbeaches, of which there are so many examples in the American Continent. This is in Churchill county, in Nevada, twenty miles south of Stillwater. The dune is said to be 100-400 feet in height, and four miles long. When agitation of the sand starts it sliding a noise is produced like that from telegraph wires fanned by a breeze. Trans. New York Acad. Sci. vol. iii., 1885, p. 97.

South America

Tarapaca in Chile.-Here also we have the record of a Singing Sand-hill known locally as the Rumbling Mountain. It is described by a mining engineer, W. Bollaert, who in about 1830 was employed in the neighbourhood. He says :

"On the road from Tarapaca to Guantajaya, and six miles west of the Pozo (or well) de Ramirez, is the Cerrito de Huara, a bramador, or rumbling mountain, which is an object of curiosity to the traveller, but to the Indians one rather of fear. The sounds are generally heard about sunrise. This hill is situated in a desert plain. During the day the country around is exposed to great heat ; at night there is a considerable diminution of temperature, in consequence of the hot south wind having gone to the eastward, where it gets cooled by the Andes, forming during the night the land breeze. As the sun rises the air becomes heated, expansion takes place, rapid currents and even gusts of wind are formed, which, striking upon the sides of the mountains and setting the sand in motion, cause probably the roaring or rumbling sounds in question." Journal of the Royal Geographical Society, vol. xxi., 1851, p. 104.

Copiapo in Chile.-A few years later (in June 1835) Charles Darwin, travelling in Chile, records another El Bramador or Bellower. While staying in the town of Copiapo, he heard of, but did not himself visit, a neighbouring hill, covered by sand, where the sound was produced by people ascending the slope. "One person with whom I conversed had himself heard the noise; he described it as very surprising; and he distinctly stated that, although he could not understand how it was caused, yet it was necessary to set the sand rolling down the declivity." Voyage of the " Beagle," p. 366. London, 1901.

A full description of this place appeared in Nature in July 1909 from the pen of M. H. Gray, who visited it with the British Consul, and thus narrated his experience, although he made the mistake of supposing that the sound was caused or accentuated by the existence of old silver workings below the surface of the moving sand:

"In a ravine a few miles to the west of Copiapo the sand has been carried by the sea breeze up the gully and lies at a slope equal to the flowing angle of dry sand. The place is locally known as El Punto del Diabolo, since, given conditions of time and weather, a low moaning sound, varying in intensity, can be heard for quite a quarter of a mile away. Amongst the superstitious natives the place is avoided. . . . On our arrival we found that the sands were quite silent, but on making a glissade down the slope a gradually increasing rumble was heard, which grew in volume as the sand slid away before us. As the sound increased we were subjected to an undulatory movement, so decided that it was difficult to keep one's balance."

Hawaii Islands

The Barking Sands of Kauai.--Lastly comes the remarkable case, said to have been discovered about the year 1850, of the so-called Barking Sands in one of the islands of the Hawaiian groups. Travellers in those strange and exotic scenes seem to have been largely unaware of or to have ignored the existence of this phenomenon. But they are mentioned in the works of Bates, Frink, Bird, Nordhoff, and some others. I take the following account from a newly published and official work on the Natural History of the Islands. The author writes as follows :

"The Barking Sands of Mana (in Kauai) consist of a series of wind-blown sand-hills, a half-mile or more in length, along the shore at Nahili. The bank is nearly 60 feet high, and through the action of the wind the mound is constantly advancing on the land. The front wall is quite steep. The white sand, which is composed of coral, shells, and particles of lava, has the peculiar property, when very dry, of emitting a sound, when two handfuls are clapped together, that, to the imaginative mind, seems to resemble the barking of a dog. When a horse is rushed down the steep incline of the mound a curious sound as of subterranean thunder is produced. The sound varies with the degree of heat, the dryness or amount of friction employed, so that sounds varying from a faint rustle to a deep rumble may be produced. Attempts at explaining this rare natural phenomenon have left much of the mystery still unsolved. However, the dry sand doubtless has a resonant quality that is the basis of the peculiar manifestation, which disappears when the sand is wet. That the Barking Sands are found in only a couple of the driest localities in the group is also significant. Much of the shoreline of Kauai, for example, is lined with old coral reefs that have partly disintegrated into sand that forms the beaches." W. A. Bryan, Natural History of Hawaii, p. 108. Hawaii, 1915. Vide also J. Blake, Proc. Calif. Acad. Sci., 1873-5, vol. v. pp. 357-8.

Dr. H. C. Bolton visited these sands in the spring of 1890 and thus described his experience:

"At its steepest part, the angle being quite uniformly 31', the sand has a notable mobility when perfectly dry, and, on disturbing its equilibrium, it rolls in wavelets down the incline, emitting at the same time a deep bass note of a tremulous character. My companion thought the sound resembled the hum of a buzz-saw in a planing mill. . . . The drier the sand the louder the sound."

Kaluakahua.-Pursuing his investigations, Dr. Bolton discovered another Sonorous Sand-dune at a place called Kaluakahua in the neighbouring islet of Niihau in the same group. Here the music is heard on the land side of a dune about 100 feet high, and at several points along the coast. " On the chief slope, 36 feet high, the sand has the same mobility, lies at the same angle, and gives when disturbed the same note as the sand of Kauai, but less strong, the slope being so much lower." Trans. New York Acad. Sci. vol. x. 1890, pp. 28-30.

Dr. Bolton added, as demonstrating that the acoustic property is independent of material, that, whereas admittedly the Sonorous Sands of all other known localities are siliceous, being either pure silex or a mixture of the same with silicates, such as feldspar, the Hawaiian sands are wholly carbonate of lime.

I have now completed my summary of the various localities in different and widely scattered parts of the world, where the phenomenon of the Singing Sands, either in steeply sloping sand-hills or in dunes, has been or still is heard ; and I have shown that instead of there being only two or at the most three spots, as the majority of writers have alleged, where it exists, it is on the contrary widely diffused, and is to be found in both hemispheres and in every continent, except, as it seems, that of Europe, where the general paucity of sand, except in the neighbourhood of the sea, and the climatic conditions are presumably unfavourable to its reproduction.

I have also, I think, collected a body of evidence sufficient to allow of certain definite deductions to be drawn, both as to the cause of the phenomenon and the conditions under which it is most likely to be produced.

Firstly, let me deal with what I may describe as the predisposing, though not always indispensable, factors. These are to be found in a number of conditions-viz. geographical situation, orientation of sand-hill, slope of sand-hill, composition of sand, climatic or meteorological features. We can then proceed to an analysis of the sounds produced, and of the mechanical or other causes that produce them.

Although the music is heard from sand-slopes or dunes of varying height and dimensions, it undoubtedly appears that it is loudest and most renowned in the case of sand-hills piled up to a considerable height against a background of cliffs or rocks ; these act in some cases as a sounding-board to the music, echoing and deepening the tones. We find this theatre of rocks existing in the case of the Chinese Rumbling Hill, the two Afghan Moving Sands, the Arabian hills of Jebel Nakus and Jebel-ut-Tabul, and probably in other cases. Against this background the sand, partly derived from disintegration of the rocks, partly swept up by the winds from the lower level, is deposited by the gales in a sloping bank, as a rule narrow at the summit and broadening as it descends. Sometimes the sand is blown over the top of the scarp by a wind from the opposite quarter. In certain of the localities there appears to be something either in the configuration of the ground or in the action of the wind that results in the concentration of the sand on the particular site where the sound is produced as distinct from any neighbouring spot. The principal sounding sand-hills in this categorv seem, as a rule, if not invariably, to face towards either the south or west-south-west. We hear sometimes of the sound as emanating from sand patches with another orientation, but in those cases the sound is much feebler. In other words, the action of the sun, beating continuously upon the surface of the sand, and causing dryness, is a material factor in the predisposing conditions.

Different authorities have given different figures - doubtless arrived at without measurement and as the result of a rough shot - for the angle of inclination of the musical slope. Some say 40', others 50'. The more careful examination of Professor Palmer and Dr. Bolton showed that the angle of Jebel Nakus is 31', which is the natural angle of rest of sand; and this is the figure, supported bv other examples, which we may accept as the normal factor in the case.

In cases where the sand-slope rests against a wall of rock, from the decomposition of which the sand is partially formed, it is noticeable that these rocks are almost always, if not always, of a light-coloured friable sandstone, mingled sometimes with limestone. Similarly the sonorous sand itself is of the same or a similar composition, being yellow or whitish in colour and consisting of mainly quartz grains. The chemical composition of the sand probably does not differ materially in any of the Sonorous Sand-hills, whether in Asia or Africa. The Barking Sands of Kauai are in a rather different category, being, not quartz, but coral-sand and shell-sand, with 95 per cent calcite. In every case there is a complete absence of very fine particles of silt, and dunes where there is much shaly matter are not musical, although other conditions may be favourable.

Although the sound is heard at different times of the year, it is not surprising-viewing the large part that heat and dryness play in the production - that the dry season is regarded as the most favourable time, at least in those parts of the world where there are great variations of climate. Where there is a tolerably uniform degree of heat in the daytime, the precise season will be less material.

It is difficult to determine the exact part which the wind may or does play in evoking the acoustic property of the sand. There can be no doubt that, where the music is heard in circumstances which admit of no mechanical or artificial causation, the wind is capable by itself of playing upon the chords, and producing the vibration that is necessary for the manufacture of the sound. This is the explanation of the fortuitous occurrence of the phenomenon. Whether the music is louder when the wind blows from a certain quarter is not certain, although some of our observers appear to have thought that this was so. Lieutenant Newbold in particular, who was a man of scientific attainments, and whose account of Jebel Nakus is the best that we possess, was of opinion that the action and direction of the wind were important factors, and that experiment should be made to ascertain the wind conditions that were most propitious to sound production.

Differing from the case of the Singing Beaches, to which I shall come presently - where dryness after moisture appears to be the most favourable condition - it would seem that in the case of the Musical Sand-hills the drier the sand the more likely the phenomenon. Rain having fallen a short time before Lieutenant Wellsted's second visit to Jebel Nakus, and the sand being still consolidated by the moisture, he did not hear the music at all. Professor Palmer, at the same spot, found that the cool or shaded sand produced only the faintest noise, while the dry and exposed parts gave forth a loud reverberation. Only in the case of the Libyan sands do we hear of the music as following upon rain, and here the description is far from conclusive. It may, I think, therefore be generally accepted that the warmth of the air, and the consequent dryness of the sand, resulting in incoherency of the sand-grains, are elements of value in the case.

And now I come to the sound itself. A few writers have made fun of the varying reports and the conflicting similes of the writers who have heard the music. I, on the contrary, am impressed by their similarity and agreement. We all know how difficult in practice it is to identify a sound, for which no obvious or artificial cause is forthcoming, with the notes of this or that musical instrument. One man will find a likeness here, another there; and this is all the more easy if the sound itself that is the subject of the comparison differs materially not only at different times, but at different moments of the same time. For nothing can, I think, be more clear in the case of the Singing Sand-hills than that they have different notes, dependent upon the degree of vibration set up in the sand-grains by the force of the external impulse communicated to them. The music seems to pass through at least three distinct phases or gradations. First there is the faintly murmurous or wailing or moaning sound, compared sometimes to the strain of an AEolian harp, at others to the humming of a top or the singing of a telegraph wire, or, when deeper, to the chords of a violoncello. Then as the vibration increases and the sound swells, we have the comparison sometimes to an organ, sometimes to the deep clangour of a bell, more frequently, in the case of the ancients, to the more resonant musical instruments with which they were familiar, namely, trumpets and kettle-drums. Finally, we have the rumble of distant thunder when the soil is in violent oscillation and the sand-grains are striking each other sharply as they glide into the vacant spaces. Because one auditor hears the fainter as compared with the louder music, there is no reason for accusing the witness to the latter of exaggeration.

The evidence also seems to be clear that the music can be heard at a great distance. Native witnesses testify to a distance of many miles. But trained and credible European observers have more than once spoken of a mile. The conditions under which the phenomenon has hitherto been investigated have not been favourable to the collection of scientific data of this supplementary type. Probably as time passes there will be a greater disposition, and perhaps fuller opportunities, to procure them.

Another interesting feature, about which it is at present impossible to dogmatise, is the length of time for which the music is heard. Few of our observers have been definite upon this point ; and doubtless it is in large measure dependent upon the degree of vibration set up and the continuance or suspension of the determining cause. Captain Lovett reported of the Seistan phenomenon that " it was said sometimes to last as long as an hour at a time." Newbold spoke of the cessation of the sound, which was coextensive with the movement of the sand, as having taken place after a quarter of an hour. Here again more scientific research will be of value.

Further, the vibratory motion of the sands is capable of being communicated to the observer. Professor Palmer, at Jebel Nakus, when he swept portions of the sand rapidly forward with his arm, felt a peculiar tingling sensation. Lieutenant Newbold spoke of the sensations produced by the vibrations as extraordinary. Lieutenant Wellsted described the rock as vibrating powerfully. Other observers, standing on the sands, while the music is sounding, have experienced similar vibrations. The Englishmen who visited El Bramador at Copiapo were so shaken by the oscillation of the sounding sand that they could scarcely stand. The American scientists record a tingling sensation in the feet or hands, when treading on or striking the Musical Sand Beaches, to which I shall presently turn.

Those who have followed me thus far will have no difficulty in arriving at an opinion as to how the sound is produced. We may roughly describe the causes of production as three in number. First, there are the occasions when the music is heard, without any visible or extraneous cause, i.e. when the sand vibrations are set up by extreme heat or drought. The Mohammedans of course attempt to connect these manifestations with their Sunday, which is our Friday; but he would be an unwise investigator who confined his visits to those occasions. Secondly, comes the direct action of the wind, setting the sand particles in continuous but not violent motion and producing a murmuring or droning sound. Thirdly, is the direct intervention of artificial agents, taking the form as a rule of men or animals treading upon the surface, either when climbing the sandslope or - which is easier - trampling down it, and producing the abrupt commotion which is the cause of the acute surface vibration noticed by some travellers, and of the long thunderous reverberations rolling and bellowing in the underground chambers. What the direct causes are, apart from wind, the casual passage of wild animals, or the accidental fall of rocks (where there are rocks), which produce the sound at night, if it is really heard then, it is more difficult to determine.

We can realise also how the actual sound is produced. As the surface is disturbed, the sand descends in gliding, sliding festoons, the music deepening as the undulations spread and the sand-grains rub and clash against each other in the course of their fall. The to-and-fro motion of the sand-grains sends out equally-spaced waves into the air with a frequency exceeding forty vibrations a second and probably very much greater. It may seem strange that the slight noise produced by the falling together of sand-grains should be able to swell to the note of a trumpet or the roar of thunder ; but it is not inappropriate to refer to the analogous case of the avalanche, where causes the most minute can produce a final effect which is colossal.

It does not appear that the movement of the sand makes any material alteration in the extent or contour of the slope, for, as the vacuum is created and the sand descends, the empty spaces fill up again from below, equilibrium is reestablished, and the shape of the sand-hill remains as before.

Why the resonance should be evoked at one attempt, and should refuse to respond at the next, must be due to some local and accidental variation in the condition of the sand or in the impulse communicated by the external agent, which it is impossible to determine with exactitude. For instance, if the sand has been trampled upon on one day, it may no longer lie at the angle of rest, and may not become musical again until, helped by wind and gravity, it has resumed the necessary conditions.

The restriction of the sound to so apparently limited a number of places (though I suspect that this is in the main the result of imperfect observation) and the silence of the sand in others (apart from the physical differences of site and surroundings and climate) must, I think, be attributable to some essential quality or conformation in the sand-grains themselves. As will be seen later on, experiments in the case of Singing Beaches have shown that their vocality is produced when the grains are of a certain size and uniformity and shape, so that they can strike against each other with the minimum of disturbance. And it may well be that some such distinctive properties are required of the sandgrains in the Singing Hills and dunes. Here again scientific researches might lead to more definite conclusions.

II. MUSICAL BEACHES

I now pass to the consideration of another branch of the problem, viz. that of the Musical Sands to be found in many places both in Europe and America, and I doubt not (were they searched for) elsewhere, on the beaches of lakes or the shores of the sea. I distinguish these sharply from the class which I have hitherto been examining, because (a) the physical conditions in which the sound is produced are quite different; (b) the acoustic Phenomena are on a far smaller and quite inconsiderable scale ; (c) they are caused not by dislodgment of comparatively large masses of sand, striking against each other, and humming or booming as they collide and fall, but by properties inherent, either permanently or transiently, in the sand, and capable of excitement by a number of still obscure causes usually involving some form of impact or compression.

Island of Eigg

The first of these Musical Sands to be discovered and seriously noted upon in modern times was that in the Bay of Laig in the little island of Eigg in the Hebrides. Hugh Miller, the well-known geologist, discovered this Singing Beach in 1845, and described it, when struck by the foot, particularly obliquely, as emitting at each step " a shrill sonorous note, somewhat resembling that produced by a waxed thread when tightened between the teeth and the hand and tipped by the nail of the forefinger." He added : " As we marched over the drier tracts, an incessant woo, woo, woo rose from the surface, that might be heard in the calm some twenty or thirty yards away; and we found that where a damp semi-coherent stratum lay at the depth of three or four inches beneath, and all was dry and incoherent above, the tones were loudest and sharpest and most easily evoked by the foot." The Cruise of the " Betsey," or A Summer Ramble among the Hebrides, p. 58. London, 1858.

The Eigg beach has since been visited by most of the experts who have been interested in the subject. They have reported the sand as white in colour, and as composed chiefly of quartz with grains of shell, magnetite, silicified wood, etc. When specimens have been taken away and experimented with, they have retained their musical character, though, after being wetted, they become immediately mute.

Studland Bay

C. Carus-Wilson, who has been the principal British student of the phenomenon of Sonorous Sands, has also reported upon a Musical Sandpatch at Studland Bay in Dorset. "The patch averaged 7 1/2 yards in width and ran parallel with the trend of the shore for some hundreds of yards. The sand on the sea side of the patch was fine, and emitted notes of a high pitch ; that on the land side was coarse, and emitted notes of a lower pitch." This sand also retained its musical quality after being taken off the patch and experimented upon, i.e. struck at home." Nature (London), vol. xxxviii., 1 888, pp. 415-540, vol. xlix., 1891, p. 322, and vol. lxxxvi., 1911, p. 518. The author had first mooted the subject in a paper entitled " Musical Sand," read before the Bournemouth Society of Natural Science on November 2, 1888, and published at Poole. Vide also Discovery, No. 5, 1920, pp. 156-8.

Other English Beaches

Patches of Musical Sand have been reported at other places along the English coast, eg. at Tenby and near Barmouth, <Nature, June 1911, p. 484.> and also at Lunan Bay, Forfar . <Ibid. vol. xxxviii., 1888, p. 515.> I do not doubt that they exist in many other localities and only await discovery.

Baltic Beaches

Other Singing Beaches in Europe are those on the Island of Bornholm, belonging to Denmark, and of Kolberg in Prussia on the Baltic. Here, as at Studland, only small tracts of the sand possess the acoustic property, and it is transient in its operation. Dr. Berendt, who investigated the phenomenon, attributed it to the saline crust on the beach. But this theory is discountenanced by the fact that precisely the same results are produced elsewhere, where there are no sea and no salt. Sands from both these places were procured by the American researchers, Dr. H. C. Bolton and Dr. A. A. Julien, and experimented upon in the course of their studies in 1884. <Trans. New York Acad. Sci. vol. iii., 1885, pp. 97-9.>

American Beaches

By far the most famous of the Musical Beaches are those which have been found in great numbers - probably owing to the superior activity of the American inquirers - in the continent of America, and notably on the shores of Lake Michigan. The dune region extends along the eastern shore of the lake from Gary at the southern extremity t o Mackinac at the northern, with few interruptions. Throughout the region the sands near the water's edge, in dry weather, emit a peculiar, but definite and unmistakable, sound, when the foot of the pedestrian pushes through them in an abrasive way. The sound is produced not only by the leather-shod foot, but is emitted also if the bare foot or hand is struck through the grains, or if a stick is trailed behind. <W. D. Richardson in Science, vol. I., 1919, p. 493.>

The latest description of the Michigan Sands is contained in a paper by W. D. Richardson in 1919. He writes as follows :

"The sound has been compared to that produced by the pedestrian walking through soft snow ; to the crunching noise so frequently noticed when walking through snow after very cold weather or by the wheel of a vehicle on such snow; also to the sound emitted by hard, granular snow when one walks through it; but it is like none of these and has a distinctive character all its own.

The sound is produced only when the sand is dry, and apparently the dryer the sand is the louder the sound produced. In wet weather or when the sand is moderately moist, the sound is not produced. In summer and indeed in the hottest weather the sound seems to be loudest, other conditions being the same, but it can be clearly heard at all seasons of the year, including winter, whenever the sand is dry. As one walks away from the water's edge he may be astonished to find out that the sound-producing sand ceases rather abruptly about 50 to 100 feet from the shore line. These limits may vary at different locations, but on the whole they are substantially correct. Back and away from the shore line, in blow-outs and on the sides and tops of the dunes, the sound is never produced. There is no observable difference between the sand located near the shore and that located farther back or that forming the dunes, and indeed the sand which is washed up by the waves is that which, blown by the wind, goes to form the dunes.

The upper beach limit of the singing sands is practically identical with the upper wave limit, that is, the boundary reached by the waves during storms. This limit is marked roughly by the line of driftwood and the lower limit of vegetation. The singing sands are, therefore, all subjected to periodical contact with the water of the lake and are moistened and washed by that water.

These observations include, I think, all the obvious ones in connection with the singing sands. The most casual observer will remark with astonishment their very sharply defined upper limit. As one walks from the water's edge up the beach and crosses the upper wave limit he notices a sudden cessation of sound as he passes the upper line of driftwood and the commencement of vegetation. Beyond this point he may proceed into a blow-out of clear sand quite identical in appearance, macroscopic as well as microscopic, and of the same composition by ordinary methods of analysis, and yet this sand fails entirely to produce the sound of the beach sand. His first conclusion would be that the proximity of the water and waves of the lake must have some relationship to the sound-producing grains." Science, vol. I., 1919, p. 493.

An, equally famous beach is that of Manchesterby-Sea, Mass., which has been a good deal written about. Thoreau is the first writer whose record of the Manchester Beach 1 have encountered. He visited it in September 1858.

"One mile south-east of the village of Manchester we struck the beach of musical sand. . . . We found the same kind of sand on a similar but shorter beach on the cast side of Eagle Head. We first perceived the sound when we scratched with an umbrella or the finger swiftly and forcibly through the sand; also still louder when we struck forcibly with our heels, " scuffling " along. The wet or damp sand yielded no peculiar sound, nor did that which lay loose and deep next the bank, but only the more compact and drv. The sound was not at all musical, nor was it loud. . . . R., who had not heard it, was about right when he said it was like that made by rubbing wet glass with your finger. I thought it as much like the sound made in waxing a table as anything. It was a squeaking sound, as of one particle rubbing on another. I should say it was merely the result of the friction of peculiarly formed and constituted particles. The surf was high and made a great noise, yet I could hear the sound made by my companion's heels two or three rods distant, and if it had been still, probably could have heard it five or six rods." " Autumn," from the Journal of H. D. Thoreau, p. 493. Boston, 1886.

Drs. Bolton and Julien, visiting the Manchester Beach in 1883, described it as a small crescent, three-quarters of a mile in length, and added:

"When struck by the foot or stroked by the hand it yields a peculiar sound which may be likened to a subdued crushing. The sound is of low intensity and pitch, and is non-metallic, non-cracking. This phenomenon is confined to that part of the beach lying between waterline and the loose sand above the reach of ordinary high tide. Some parts of the beach emit a louder sound than others. The Sounding Sand is near the surface only. At the depth of 1 or 2 feet the acoustic properties disappear, probably owing to the moisture. Only the dry sand has this property. The sounds occur when walking over the beach, increase when the sand is struck obliquely by the foot, and can be intensified by dragging over it a wooden pole or board. A slight noise is perceptible upon mere stirring by the hand, or upon plunging one finger into the sand and suddenly withdrawing it." Proceedings of the American Association for the Advancement of Science, vol. xxxii., 1883, p. 251.

Yet another American Singing Beach is that of Far Rockaway, on Long Island, a sample of the sand of which, when removed from a bottle in which it had lain undisturbed for thirty-five years, poured into a stocking, and compressed, gave out its original high note, audible at a considerable distance. This, however, after the sand had been handled, it soon lost. <Science (New York), vol. li., 1920, p. 64.>

So indefatigable were the American experts in their labours that, after a year of investigation, they had discovered, in 1884, in answer to their circulars of inquiry, no fewer than seventy-four places in the United States where the phenomenon of sonorous sand occurred. These were mostly on the Atlantic coast. In 1890, however, Dr. H. C. Bolton personally visited the Pacific coast and discovered Sounding Sands at a number of places in California. He also reported the existence of a sonorous sand-hill at the extreme southern end of the Peninsula of Lower California, where the sound produced by the sliding sand is like that of bells, and is explained by the Mexicans, like the music at Jebel Nakus, as proceeding from the bells of a monastery that once existed on this site, but was overwhelmed by the drifting sand. <Trans. New York Acad. of Sci. vol. x., 1890, pp. 31-5.> I entertain little doubt that similar inquiries would produce similar results in other parts of the world.

Costa Rica

At one of the meetings of the New York Academy of Sciences in March 1884, after an account by Dr. Julien of his visits to Eigg and to Manchester-by-Sea and other American sites, a visitor arose and described his experience on the shore of Costa Rica, on the Caribbean Sea, about seventeen miles south of Greytown, in 1864, where he had heard at 11 P.m. on successive nights sounds from the sea-beach that were " sometimes like a low roar or the barking of a dog, sometimes like the voices of men conversing, sometimes like hundreds of loud voices in the air, sometimes like singing, sometimes like the stringing of chords." He had attributed these sounds to the fact that the sand lay upon a coral reef, fissured by very deep clefts, and he had thought at first that it must be due to the movement of sea water in the hollows ; but he now thought it must have been the sand. <Trans. New York Acad. of Sci. vol. iii., 1885, p. 73.> It will be remembered that the Barking Sands of Kauai are mainly composed of disintegrated coral.

Other Musical Beaches

The continuous studies of the American experts have revealed the existence of the same phenomenon in such widely different parts of the world as Botany Bay, New South Wales; Brown's River Bay, Tasmania; Cape Ledo, and Liberia, West Africa. In fact, I do not doubt that musical sand is frequent in both hemispheres, and only lacks the discoverer or the reporter to become much more widely known.

It will have been seen how widely different are these phenomena from that of the larger and more vocal group of sand-hills and sand-slopes before described. The former share with the latter the common feature of vocality arising from the vibration of sand-grains set in motion, but (a) they are found only on the shores of seas or lakes, and in a few recorded cases on the banks of rivers, < Trans. New York Acad. of Sci. vol. x., 1890, pp. 33-5.> but not, so far as I know, on horizontal sand-patches in the interior; (b) the displacement of the sand-grains requires to be only of the slightest, in order to evoke the sound ; (c) the nature of the sound, in respect of pitch and volume, is insignificant compared with the kettledrums and trumpets, the thundering and rumbling, of the great sand-hills ; (d) the acoustic property, given a certain degree of dryness and warmth, seems to be very consistent in its presence and action.

When we come to a scientific explanation of the exact causes which produce the vibration and therefore the sound, we are in an area of greater speculation, for I find that no two experts wholly agree. Among the theories which have been advanced, but which, though sufficient in some cases, seem to be inapplicable in others, are equality of size of sand-grains, resonance due to cellular structure, effervescence of air between moistened surfaces, solarisation, reverberation within subterranean cavities, electrical phenomena.

The result of the experiments made by C. Carus-Wilson was to convince him that the phenomenon of Musical Sands is found (1) where the grains are rounded, polished, and free from fine fragments; (2) where they have a sufficient amount of " play " to enable them to slide or rub one against the other; (3) where the grains are perfectly clean ; and (4) where they possess a certain degree of uniformity in size, and are within a certain range of size. <Nature, vol. lxiv., 1891, p. 322.> If these conditions are satisfied, and if the grains, rubbing against each other, produce a number of vibrations of equal length, then the musical note results. Elsewhere he says that the notes are due to " the rubbing together of millions of clean and incoherent grains of quartz, with no angularities, roughness, or adherent matter investing the grains; and that, though the vibrations emitted by the friction of any two grains might be inaudible, those issuing from millions approximately of the same size would give an audible note." Discovery, No. 5, 1920, p. 157.

On the other hand, the American researchers, Drs. Bolton and Julien, rejected all these hypotheses <They said that Mr. Wilson's theory might fairly explain squeaking sand, but was insufficient to explain musical sand. They reported the former as existing in two places only, both in so-called boiling springs - one in Maine, the other in Kansas - where a shrill squeaking sound is produced by attrition when the sand is moist. This is, of course, quite a different phenomenon.> and, after years of study, arrived at the following conclusion :

"The true cause of the sonorous property is connected with thin pellicles or films of air or of gases thence derived, deposited, and condensed upon the surface of the sand-grains during gradual evaporation, after wetting by the sea, lakes, or rains. By virtue of these films the sand - grains become separated by elastic cushions of condensed gases, capable of considerable vibration. The extent of the vibration and the amount and tone of the sound thereby produced, after any quick disturbance of the sand, is largely dependent upon the forms, structures, and surfaces of the sand-grains, and especially upon their purity or freedom from fine silt or dust." < Trans. New York Acad. Sci. vol. viii. p. 10. Ibid. vol. x., 1890, pp. 28-35.>

The American experts would, I understand, apply this hypothesis to the explanation of all sonorous sands, whether on sea or lake shores or in the deserts. In other words, they postulate everywhere some degree of previous moisture, induced or exhausted by evaporation. This would indeed appear to be probable enough in the case of beach sands, and is supported by experiments showing that the singing quality of such sands is apt to become extinct after they have dried out.

How far this theory is applicable to the big sonorous sand-hills cannot be ascertained without meteorological data that are at present lacking. But I cannot help thinking that in the majority of the cases cited in the earlier part of this essay rainfall must be a very rare phenomenon, while in only one record of a successful visit is there any mention of previous shower or storm. That sonorousness anywhere is largely dependent upon meteorological conditions, i.e. the dryness or moisture of the atmosphere, is a less contestable proposition.

I should add that Drs. Bolton and Julien have never, to the best of my knowledge, published any experimental proof of the validity of their explanation, which is not generally accepted.

Another explanation is offered by Professor J. H. Poynting and Sir J. Thomson in their "Treatise on Sound," <Text-Book of Physics. London, 1913.> based on a paper by Professor Osborne Reynolds, "On the Dilatancy of Media composed of Rigid Particles in Contact." <Phil. Mag. Ser. 5, vol. xx., 1885, pp. 469-81.>

Reynolds showed that in granular media in which the grains are sensibly hard, so long as the grains are held in mutual equilibrium by stresses transmitted through the mass, every change of relative position of the grains is attended by a consequent change of volume. For such granular medium he assumed that the position of any internal particle becomes fixed when the positions of the surrounding particles are fixed : a condition which is very generally fulfilled unless there is considerable friction. It follows from this that no grain in the interior can change its position without disturbing the contiguous grains; hence in a medium in which the friction is sufficiently small the movement of any one grain in the medium involves the movement of every other grain in the medium.

The explanation offered by Poynting and Thomson is as follows : "There is an arrangement of minimum volume for a number of equal spheres in contact. We may suppose the sand to consist of equal spheres arranged, when undisturbed, so as to occupy minimum volume. When disturbed the mass may pass through many successive minima of volume before coming to rest, and if we can suppose the time occupied in passing from one minimum to the next is constant, a musical note should issue."

The condition that the grains are spherical is not an essential one, but such an assumption assists the imagination and facilitates calculations. The essential conditions will be that friction shall be low, and that the time occupied in passing from one minimum to another shall be constant - which implies uniformity of grain.

This explanation seems to be reasonable, but has not as yet been definitely proved by experiment. A slight adaptation of Carus-Wilson's idea that the sound is due to the rubbing together of millions of sand-grains of approximately the same size may lead us to a possible cause, or at least to a contributory cause, of the musical notes, and will give a note the pitch of which depends in the same way on grain-size and rate of displacement as does the frequency of the volume changes.

If the displacement of any one grain involves the displacement of all the others in the mass, we have millions of grains undergoing similar displacements at the same instant. The displacement involves the repeated pushing of one grain over the next below it into the depression beyond. If we can imagine each grain falling over the edge of the grain below, striking the next grain with a little impact, and repeating this with perfect regularity every time it changes its position, we have a cause for a regular train of equally spaced sound-waves which, when of sufficiently high frequency, will give a musical note. The periods of the impacts will be identical with the periods between successive minima of volume in the Poynting and Thomson theory. The two effects may go on simultaneously, and will produce notes of the same pitch. The Poynting and Thomson volume-change is no doubt mainly responsible for the musical notes, but it is difficult to tell to what extent the actual contact of the grains is contributory to the sound.

And so, in this rather nebulous phase of speculative uncertainty, I leave the Sounding Sands to continue their mysterious song, confining their favours to the lucky few, and exciting the curiosity, but, I hope, no longer the incredulity, of the remainder. That they exist in their greater as well as in their lesser manifestations will not be contested. That their music covers a wide diapason of sound, from the twanging of a string or the humming of a wire to the rumbling of thunder and reverberation of drums, has been shown. That the phenomenon is to be explained in every case by natural causes is indisputable. And if I am conscious of not having found a common theory to account irrefutably for all examples, it is, in my belief, because no such theory can be made to apply; while in the inability to formulate it with exactitude I am sustained by the reflection that I am in the company of all the learned professors, who, like most professors, disagree, but who may perhaps be grateful to me for having given a synthesis of the problem that may provoke their renewed examination.

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