214 FRAGMENTS OF SCIENCE. 
and removing the sensitive flame to/', some distance be- 
hind 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 tb.e heterogeneous 
air threw the sensitive flame into violent 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 
the suggestion of Professor Dewar, Mr. McRoberts has 
carried out a series of experiments on dynamite, with 
extremely promising results. Immediately after the 
delivery of the foregoing lecture I was informed that Mr. 
Brock proposed the employment of dynamite in the 
Gollinsou rocket. 
