1889.] NEW YORK ACADEMY OF SCIENCES. 23 



ranean monastery in the heart of the mountain, and claim that 

 the sounds can only be heard at tiie hours of prayer. 



Several other sand-banks, presenting a similar appearance to 

 the eye, were tested, but gave out no musical sounds whatever. 

 Microscopical examination of the sand shows that it contains 

 much silt, which prevents the vibrations necessary to yield the 

 sounds. After careful study, however, of Seetzen's Bell Slope, 

 I became convinced that the phenomena could not be unique in 

 the desert, as supposed; and hence I made systematic search for 

 another locality. After testing many sand-banks on the journey 

 northwai'd to Suez, I discovered, on April 6th, banks of sonorous 

 sand resting on low cliffs a quarter of a mile long. This new 

 locality is in Wadi Werdan, about a day and a half from Suez 

 by camels, and is on hillocks called Ojrat Ramadan. 



The sand blown from the extensive plains to the north falls 

 over the southern face and rests at two angles, 31° at the top 

 and 21° or less near the base. Wherever it possesses the mobil- 

 ity before described, it emits a distinct musical note on being 

 disturbed. The highest bank measures only. sixty feet on the 

 incline, and it is not probable that the sounds can occur spon- 

 taneously. Dr. Julien has named the new locality Bolton's Bell 

 Slope, and reports that microscopical examination shows the 

 sand to consist chiefly of quartz grains, and a larger proportion 

 of calcareous sandstone than at Jebel Nagous. The size of the 

 grains of quartz varies from 0.11 to 0.42 mm. and of sandstone 

 0.11 to 0.34 mm., — the average being smaller than that of the 

 sand-grains on Jebel Nagous. Like the latter, it is very free 

 from silt. 



Various hypotheses have been proposed to explain the cause 

 of the sonorous jDroperty in certain sands. Sir James Prinsep, 

 Secretary of the Asiatic Society of Calcutta, attributes the sound 

 l^roduced at Jebel Nagous to a "■ reduplication of impulses set- 

 ting air in vibration in a focus of echo." 



Hugh Miller, after his visit to the singing beach at Eigg, in- 

 terested his friend, Sir David Brewster, in the problem, and he 

 wrote of " accumulated vibrations of the air when struck by the 

 driven sand, or the accumulated sounds occasioned by the mutual 

 impact of the particles against each other." The sonorousness 

 of the sand at Kauai has been attributed to the cellular character 

 of the coralline material; that of Jebel Nagous to its essentially 

 quartzose nature; that of the Baltic coast of Prussia to the 

 saline crust on the beach (Dr. Berendt); but the researches of 

 Dr. Julien and myself show that the sonorous property is inde- 

 pendent of material and of saline waters. Many other explana- 

 tions have been offered, which we can here but briefly name: — 

 electricity; effervescence of air between moistened grains; solari- 



