280 FKAGMENTS OF SCIENCE. 



tranquilly, though the reed was sounding. Again 

 lighting the gas as it issued from the brass tubes, 

 the sound reflected from the 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 

 substance 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. Immedi- 

 ately after the delivery of the foregoing lecture I. was 

 informed that Mr. Brock proposed the employment of 

 dynamite in the Collinson rocket. 



