Account of the Granite Qiiarries at Assuan. 5S 



under the rocks where the pilgrims are in the habit of placing 

 themselves to listen. 



*' In climbing, I heard the sound from beneath my knees, 

 and this made me think that the sliding of the sand was the 

 cause, and not the effect of the sonorous motion. At three 

 o'clock the sound was heard louder, and it lasted six minutes, 

 when, having ceased for ten minutes, it began again. It ap- 

 peared to me to have the greatest analogy to the humming top ; 

 it rose and fell like the sound of an Eolian harp. To ascer- 

 tain the truth of my discovery, I climbed with the utmost 

 difficulty to the highest rocks, and I slid down as fast as I 

 could, and endeavoured, with the help of my hands and feet, 

 to set the sand in motion. 



" This produced an effect so great, and the sand in rolling 

 under me made so loud a noise, that the earth seemed to tremble, 

 and I should certainly have been afraid, had I been ignorant 

 of the cause. 



" But how can the motion of the sand produce so striking an 

 effect, and which is, I believe, observed nowhere else ? Does 

 the rolling layer of sand act like the fiddle-bow, which, on be- 

 ing rubbed upon a plate of glass, raises and distributes into 

 determinate figures the dust with which the plate is covered? 

 Does the adherent and fixed layer of sand perform here the 

 part of the plate of glass, and the neighbouring rocks that of 

 the sounding body ? Philosophers must decide this. My 

 journal contains a more detailed account of this phenomenon, 

 and a rough draught of the rocks of Nakous. I have in my 

 mineralogical collection specimens of the sandstone, as well 

 as the moveable sand which is found at this place." — Monatt 

 liche Correspondenzy October 1812, p. 393. '* 



3. Account of the Granite Quarries at Assuan. By the Honour- 

 able C. L. Ikby, and James Mangles, Esq. Commanders 

 in the Navy. 



" On our arrival at Assuan, we proceeded to visit the ancient 

 granite quarries in the neighbourhood. Our principal object 

 was to examine the column which is there, and which has an 

 inscription in Latin not devoid of interest. Our guide lost, 

 his way at first, and took us to another part of the quarry, 



