RECENT EXPERIMENTS ON FOG-SIGNALS. 271 



some of the sounds were heard on the day now re- 

 ferred to: 



24 out of 40 sounds heard. 



The day was cloudy, with occasional showers of 

 drizzling rain; the wind about N.W. by N. all day; at 

 times squally, rising to a force of 6 or 7 and sometimes 

 dropping to a force of 2 or 3. The station at Leigh 

 excepted, all these places were to leeward of Shoebury- 

 ness. At four other stations to leeward, varying in 

 distance from 15 to 24 miles, nothing was heard, 

 while at eleven stations to windward, varying from 8 to 

 26 miles, the sounds were also inaudible. It was found, 

 indeed, that the sounds proceeding directly against the 

 wind did not penetrate much beyond 3 miles. 



On the following day, viz. the 18th October, we 

 proceeded to Dungeness with the view of making a 

 series of strict comparative experiments with gun- 

 cotton and cotton-powder. Rockets containing 8 oz., 

 4 oz., and 2 oz. of gun-cotton had been prepared at the 

 Royal Arsenal; while others, containing similar quan- 

 tities of cotton-powder, had been supplied by the Cot- 

 ton-powder Company at Faversham. With these were 

 compared the ordinary 18-pounder gun, which hap- 

 pened to be mounted at Dungeness, firing the usual 

 charge of 3 Ibs. of powder, and a syren. 



From these experiments it appeared that the gun- 

 cotton and cotton-powder were practically equal as 

 producers of sound. 



