MUSICAL MOUNTAIN OF EL-NAKOUS. 299 



He could not observe any crevices by which the external 

 air could penetrate, and as the sky was serene and the air 

 calm, he was satisfied that the sounds could not arise from 

 this cause.* 



* See Edinburgh Journal of Science, No. xi. p. 153, and No. xiii. 

 p. 51. 



