276 FRAGMENTS OF SCIENCE. 



course of the sound, the echo from the broadside of 

 the vessel was returned as a shock which rudely inter- 

 rupted the continuity of the dying atmospheric music. 



These echoes have been ascribed to reflection from 

 the crests of the sea-waves. But this hypothesis is 

 negatived by the fact, that the echoes were produced 

 in great intensity and duration when no waves existed 

 when the sea, in fact, was of glassy smoothness. It 

 has been also shown that the direction of the echoes 

 depended not on that of waves, real or assumed, but 

 on the direction of the axis of the trumpet. Causing 

 that axis to traverse an arc of 210, and the trumpet 

 to sound at various points of the arc, the echoes were 

 always, at all events in calm weather, returned from 

 that portion of the atmosphere towards which the 

 trumpet was directed. They could not, under the 

 circumstances, come from the glassy sea; while both 

 their variation of direction and their perfectly con- 

 tinuous fall into silence, are irreconcilable with the 

 notion that they came from fixed objects on the land. 

 They came from that portion of the atmosphere into 

 which the trumpet poured its maximum sound, and 

 fell in intensity as the direct sound penetrated to 

 greater atmospheric distances. 



The day on which our latest observations were 

 made was particularly fine. Before reaching Dunge- 

 ness, the smoothness of the sea and the serenity of the 

 air caused me to test the echoing power of the atmos- 

 phere. A single ship lay about half a mile distant 

 between us and the land. The result of the proposed 

 experiment was clearly foreseen. It was this. The 

 rocket being sent up, it exploded at a great height; 

 the echoes retreated in their usual fashion, becoming 

 less and less intense as. the distances of the invisible 

 surfaces of reflection from the observers increased. 



