124 MUSICAL ROCKS. 



and were supposed to have been occasioned by the transmis- 

 sion of rarefied air through the crevices of a sonorous stone, 

 like many other instances which exist of a similar phenomenon. 

 The scientific men who accompanied the French expedition 

 into Egypt heard, at sunrise, in a monument of granite in the 

 palace of Karnac, a noise resembling the breaking of a string, 

 which is the very expression used by Pausanias to describe 

 the sound of the Memnon. De Humboldt speaks in the Ori- 

 noco of musical rocks (loxas de mustca*}, which sounded at 

 sunrise; and recent travellers have given explicit accounts of 

 rocks in Arabia Petraea which also emit sounds at particular 

 hours of the day; and indeed Sir A. Smith asserts, that at six 

 o'clock in the morning. He heard very distinctly the sounds 

 issue from Memnon which had rendered it so famous in ancient 

 times. Now, in all these instances, the sound is supposed 

 to proceed from the sudden change of temperature which 

 takes place at the rising of the sun. The stones are heated 

 during the day by the action of the sun, and the difference of 

 temperature between the subterraneous and the external air at- 

 tains its maximum (or greatest difference) about sunrise, or, at 

 that moment which is furthest from the period of the greatest 

 heat of the preceding day. The sound therefore proceeds 

 from the impulse of air upon the stones; and the Egyptian 

 priests, having observed the phenomenon on some rocks in 

 Egypt, were supposed to have arranged the stones of the 

 pedestal of Memnon so as to produce this singular effect; but 

 it now appears, from the relation of Mr. Wilkinson, that on 

 ascending the statue he found that there is a stone in its lap, 

 which, upon being struck, emits a metallic sound, and which 

 might still he made use of to deceive the credulous. In the 

 block behind, is cut a squared space, as if to admit a person, 

 who might be placed there to strike the stone, and who would 

 lie concealed from the most scrutinous observer in the plain 

 below. Mr. Wilkinson is therefore convinced that this sound 

 was the same that deceived the Roman visitors,- with whose 

 description of it, it perfectly accords. f 



* Voyage, vol. vi. p. 377. t Wilkinson's Thebes, p. 97. 



