276 FKAGMENTS OF SCIENCE. 



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 Dungeness, the 

 smoothness of the sea and the serenity of the air caused 

 me to test the echoing power of the atmosphere. 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 rockpt 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. About five seconds after the 

 explosion, a single loud shock was sent back to us from 

 the side of the vessel lying between us and the land. 

 Obliterated for a moment by this more intense echo, 



