510 WRITINGS OF JOSEPH HENRY. [1877 



of tlie trumpet. The loudness of this echo depends upon the 

 loudness and quantity of the original sound, and therefore 

 it is produced with the greatest distinctness by the siren. It 

 cannot be due to the accidental position of a flocculent por- 

 tion of atmosphere, nor to the direct reflection from the 

 crests of the waves, as was at first supposed, since it is always 

 heard except when the wind is blowing a hurricane. 



As a provisional explanation, the hypothesis has been 

 adopted that in the natural spread of the waves of sound 

 some of the rays must take such a curvilinear course as to 

 strike the surface of the water in a vertical direction, and 

 thus be reflected back — by a similar deviation, to the station 

 or location of the origin of the sound. 



END OF VOL I. 



