MUSICAL SAND.
Most persons have heard of stones which on being struck give out musical notes, and many may have seen the arrangement of such stones known as the Rock Harmonicon, which is capable of discoursing eloquent music. But the existence of musical or sonorous sand is not so well known, although such sand appears to occur in localities widely distributed over the earth’s surface. A paper giving some interesting particulars respecting this phenomenon was communicated to the meeting of the American Association for the Advancement of Science at Philadelphia in 1884, by Professor Bolton of Hartford, Connecticut, and Dr Alexis Julien of New York. The authors begin their paper by stating that at the Minneapolis meeting of the Association they had given some account of the so-called ‘Singing Beach’ at Manchester-by-the-Sea, Massachusetts, and of the occurrence of sonorous sand at Eigg, in the Hebrides, and other localities. During the twelve months that had elapsed, they had continued their researches; and by means of extensive correspondence, they had established the fact, that sonorous sand, instead of being a rarity, is of very common occurrence. Circulars were sent to all keepers of life-saving stations throughout the United States; and from the replies received to date, a list of seventy-four localities in America had been obtained.
Through the Smithsonian Institution, specimens of sonorous sand had been received from the island of Bornholm, Denmark; Colberg, Prussia; and Kanai, Hawaii Islands. Experiments had been conducted both at Manchester-by-the-Sea and at Far Rockaway, Long Island, to determine accurately the properties of sonorous sand, with the object of explaining the cause of its singular characteristics. It was found that the loudest sound of which a given sand is capable was most conveniently produced by confining a quart or more in a bag and strongly striking together the contents. Sounds thus produced were heard distinctly at both the Manchester and Rockaway beaches at a distance of one hundred and fifty to two hundred feet, the distance varying according to the strength and direction of the wind and the interference of the surf-noise. At Rockaway, a careful experiment was made in fields removed from the beach. The sound produced by striking the bag was heard at a distance of four hundred and fifty feet, measured by a tape-line. The sound has a hoot-like tone, easily recognised.
The character of the sounds obtained by friction on the beach is decidedly musical, and the experimenters were able to indicate the exact notes on a musical staff. The shrillness and lowness of note depend chiefly on the quantity of sand disturbed. By plunging both hands into the sand and bringing them together quickly, a tone is heard of which the dominant note is B below the treble stave
. By stroking the sand nearer the surface and with less force, very high notes were heard confused. They ranged from E, fourth space treble clef, to B above the stave. By rubbing firmly and briskly a double handful of the sand, several notes on a rising scale were heard. The ear received an impression something like that formed by sliding a finger up a violin string at the same time that the bow is drawn. These results were obtained at Manchester. The Rockaway beach gave somewhat different tones—the B below the leger-line was not heard at all; but the note F, first space treble, B, C, and G above the stave, were heard at different times according to the manner of the friction. The notes were determined by comparison with those made on a violin, concert pitch.
The evanescent character of the acoustic quality of the sand is strongly marked. Sand which has been recently wet requires thorough drying before it resumes its acoustic powers; consequently, sandy beaches do not always possess the sonorous power in equal measure, and the seeker sometimes fails to discover musical sand in the locality reputed. Meteorological conditions decidedly affect the sonorousness.
Musical sand is easily deprived of its acoustic qualities. Besides wetting it, friction between the dry hands also accomplishes the result. The quickest way of ‘killing’ the sand—except by water—is to shake a small quantity in a tin box. When first agitated, a peculiar sound is heard, which entirely ceases after twenty to twenty-five slow up-and-down movements of the box. Attempts to restore to ‘killed’ sand its sonorous properties have met with indifferent success. Sonorous and mute sand occur in the beach closely adjoining, but they cannot be distinguished by the eye; friction alone determines the difference. In sand of strongly marked acoustic properties, a tingling sensation is perceived in the finger and also in the toe, even through the boots.
Careful search in literature shows that allusions to sonorous sand are scattered sparingly through writings of a thousand years. An obscure allusion to the phenomenon occurs in one of the stories of the Arabian Nights. Old Chinese chronicles mention sonorous sand as occurring in the desert of Lob-nor. Marco Polo narrates superstitions concerning it. The Emperor Baber refers to a locality in Afghanistan; and many travellers in the East describe hills of moving sand whence issue mysterious noises. The famous Jebel Nakous, situated on the east coast of the Gulf of Suez, has been visited by at least six European and American travellers, including Ehrenberg, who was there in 1823. By comparing their descriptions, it has been discovered that they describe not one locality, but two, or possibly three, in the same region. The dry sand rests on a steep incline, and when agitated, slides down the slope with a gradually increasing noise, variously described, but the loudest tones of which are universally compared to distant thunder. In 1850, Hugh Miller discovered musical sand at Eigg, in the Hebrides. In 1882, Professor Bolton visited the same locality and began a monograph.
Microscopical examination of the samples of musical sand showed that the great majority were remarkable for a certain degree in uniformity of size—usually about 0.3, 0.4, 0.5 millimetres in diameter, general round form, polished superficies, and freedom from fine dust or minute fragments; consequently, they often present a characteristic oolitic or roe-like appearance, light colour, and mobile condition. At certain localities, the sonorous sand has been found to present the decided features of a quicksand; and a general connection between these two facts is suspected to prevail wherever the conformation of coasts and oceanic currents permit the concentration of the sonorous sand below the high-tide mark.