:i92 FRAGMENTS OF SCIENCE 



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 rocket being sent up, it ex- 

 ploded at a great height; the echoes retreated in their 

 usual fashion, becoming less and less intense as the dis- 

 tances of the invisible surfaces of reflection from the ob- 

 servers increased. About five seconds after the explo- 

 sion, a single loud shock was sent back to us from the 

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

 ated for a moment by this more intense echo, the aerial 

 reverberation continued its retreat, dying away into silence 

 in two or three seconds afterward.* 



I have referred to the firing of an 8-oz. rocket from the 

 deck of the *' Galatea'* on March 8, 1877, stating the dura- 

 tion of its echoes to be seven seconds. Mr. Prentice, who 

 was present at the time, assured me that in his experi- 

 ments similar echoes had been frequently heard of more 

 than twice this duration. The ranges of his sounds alone 

 would render this result in the highest degree probable. 



» The echoes of the gun fired on shore this day were very bnef ; those of 

 the 12- oz. gun-cotton rocket were 12" and those of the 8-oz. cottoa-powdar 

 rocket 11" in duration. 



