RECENT EXPERIMENTS ON FOG-SIGNALS. 263 



gun-cotton detonated in free air. On this occasion 

 nineteen different series of experiments were made, 

 when the new experimental gun, firing a 3-lb. charge, 

 demonstrated its superiority over all guns previously 

 employed to fire the same charge. As regards the com- 



FJO. 8. 



Gun-cotton Slab (H lb.) Detonated in the Focus of a Cast-iron 

 Keflcctor. 



parative merits of the gun-cotton fired in the open, 

 and the gun-powder fired from the new gun, the mean 

 values of their sounds were the same. Fired in the 

 focus of the reflector, the gun-cotton clearly dominated 

 over all the other sound-producers.* 



The whole of the observations here referred to were 

 embraced by an angle of about 70, of which 50 lay on 



* The reflector was frnctured by the explosion, but it did 

 good service afterwards. 

 18 



