RECENT EXPERIMENTS ON FOG-SIGNALS 285 



In December, 1876, Mr. Gardiner, the managing director 

 of the Cotton -powder Company, had proposed a trial of 

 this material against the gun-cotton. The density of the 

 cotton he urged was only 1-03, while that of the powder 

 was 1-70. A greater quantity of explosive material being 

 thus compressed into the same volume, Mr. Gardiner 

 thought that a greater sonorous effect must be produced 

 by the powder. At the instance of Mr. Mackie, who had 

 previously gone very thoroughly into the subject, a com- 

 mittee of the Elder Brethren visited the cotton-powder 

 manufactory, on the banks of the Swale, near Faversham, 

 on the 16th of June, 1877. The weights of cotton-powder 

 employed were 2 oz., 8 oz., 1 lb., and 2 Ibs., in the form 

 of rockets and of signals fired a few feet above the 

 ground. The experiments throughout were arranged and 

 conducted by Mr. Mackie. Our desire on this occasion 

 was to get as near to windward as possible, but the Swale 

 and other obstacles limited our distance to 1% mile. We 

 stood here E.S.E. from the firing-point while the wind 

 blew fresh from the N.E. 



The cotton-powder yielded a very effective report. 

 The rockets in general had a slight advantage over the 

 same quantities of material fired near the ground. The 

 loudness of the sound was by no means proportional to 

 the quantity of the material exploded, 8 oz. yielding very 

 nearly as loud a report as 1 lb. The "aerial echoes," 

 which invariably followed the explosion of the rockets, 

 were loud and long-continued. 



On the 17th of October, 1877, another series of experi- 

 ments with howitzers and rockets was carried out at 

 Shoeburyness. The charge of the howitzer was 3 Ibs. 

 of L. G. powder. The charges of the rockets were 12 oz., 



