KECENT EXPERIMENTS ON FOG-SIGNALS. 315 



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, demon- 

 strated its superiority over all guns previously employed 

 to fire the same charge. As regards the comparative 



FIG. 10. 



Gun-cotton Slab (1 Ib.) Detonated in the Focus of a Cast-iron 

 Reflector. 



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 re- 

 flector, the gun-cotton clearly dominated over all the 

 other sound-producers. 1 



The whole of the observations here referred to were 

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

 1 The reflector was fractured by the explosion, but it did good 

 service afterwards. 



