RECENT EXPERIMENTS ON FOG-SIGNALS 287 



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 pro- 

 ceeded to Dungeness with the view of making a series of 

 strict comparative experiments with gun-cotton and cotton- 

 powder. Eockets containing 8 oz., 4 oz., and 2 oz. of 

 gun-cotton had been prepared at the Koyal Arsenal; while 

 others, containing similar quantities of cotton-powder, had 

 been supplied by the Cotton-powder Company at Faver- 

 sham. "With these were compared the ordinary 18-pounder 

 gun, which happened to be mounted at Dungeness, firing 

 the usual charge of 3 lbs. of powder, and a syren. 



From these experiments it appeared that the gun-cotton 

 and cotton-powder were practically equal as producers of 

 sound. 



The effectiveness of small charges was illustrated in a 

 very striking manner, only a single unit separating the 

 numerical value of the 8-oz. rocket from that of the 2-oz. 

 rocket. The former was recorded as 6*9 and the latter as 

 6*9, the value of the 4-oz. rocket being intermediate be- 

 tween them. These results were recorded by a number 

 of very practiced observers on board the *' Galatea." 

 They were completely borne out by the observations of 

 the Coastguard, who marked the value of the 8-oz. rocket 

 6*1, and that of the 2-oz. rocket 5*2. The 18-pounder 

 gun fell far behind all the rockets, a result, possibly, to 

 be in part ascribed to the imperfection of the powder. 

 The performance of the syren was, on the whole, less sat- 

 isfactory than that of the rocket. The instrument was 

 worked, not by steam of 70 lbs. pressure, as at the South 

 Foreland, but by compressed air, beginning with 40 lbs. 



