RECEN1 EXPERIMENTS ON FOG-SIGNALS 



295 



front of the South Foreland strikingly imitated. 1 Turning 

 off the gas, and removing the sensitive flame to /', some 

 distance behind the reed, it burned there tranquilly, 

 though the reed was sounding. Again lighting the gas 

 as it issued from the brass tubes, the sound reflected from 



Fig. 9. 



the heterogeneous air threw the sensitive flame into vio- 

 lent agitation. Here we had imitated the aerial echoes 

 heard when standing behind the syren-trumpet at the 

 South Foreland. The experiment is extremely simple, and 

 in the highest degree impressive. 



The explosive rapidity of dynamite marks it as a sub- 

 stance specially suitable for the production of sound. At 



1 "Lectures on Sound." 3d edition, p. 268. 



