Lieutenant Wellsted observed, that the shape and arrangement of the rocks resembled, in some respects, a whispering-gallery; but he ascertained, by experiment, that their irregular surface rendered them but ill-adapted for the production of an echo. Seated on a rock at the base of the sloping eminence, he directed a Bedouin to ascend; and it was not till he had reached some distance that the lieutenant 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 above, until a considerable portion of the surface was in motion. As the sand began to fall, the sounds produced might be compared to the faint strains of an Eolian harp when its strings first catch the breeze. When the sounds 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 lieutenant Wellsted was seated to vibrate; and the camels, animals not easily frightened, became so alarmed, that their drivers could only retain them with difficulty. The noise, it was remarked, 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 that bound it in that direction. The tradition is, that the bells of a convent were buried here; the Bedouins trace the sounds to several wild and fanciful causes; but, in the experiment now described, it was evident that the sounds sometimes fell quicker on the ear, and at other times were more prolonged, according to the Arab’s increasing or retarding the velocity of his descent.