204 FRAGMENTS OF SCIENCE. 



are intended to spread the sound all around them as from 

 central foci. As a signal in rock lighthouses, where 

 neither syren, steam-whistle, nor gun could be mounted; 

 and as a handy fleet-signal, dispensing with the lumber of 

 special signal -guns, the gun-cotton will prove invaluable. 

 But in most of these cases we have the drawback that local 

 damage may be done by the explosion. The lantern of the 

 rock lighthouse might suffer from concussion near at hand, 

 and though mechanical arrangements might be devised, 

 both in the case of the lighthouse and of the ship's deck, 

 to place the firing-point of the gun-cotton at a safe dis- 

 tance, no such arrangement could compete, as regards 

 simplicity and effectiveness, with the expedient of a gun- 

 cotton rocket. Had such a means of signaling existed at 

 the Bishop's Rock lighthouse, the ill-fated Schiller 

 might have been warned of her approach to danger ten, or 

 it may be twenty miles before she reached the rock which 

 wrecked her. Had the fleet possessed such a signal, 

 instead of the ubiquitous but ineffectual whistle, the 

 Iron Duke and Vanguard need never have came into 

 collison. 



It was the necessity of providing a suitable signal for 

 rock lighthouses, and of clearing obstacles which cast an 

 acoustic shadow, that suggested the idea of the gun-cotton 

 rocket to Sir Richard Oolliuson, deputy master of the 

 Trinity House. His idea was to place a disk or short cyl- 

 inder of gun-cotton in the head of a rocket, the ascensional 

 force of which should be employed to carry the disk to an 

 elevation of 1,000 feet or thereabouts, where by the ignition 

 of a fuse associated with a detonator, the gun-cotton should 

 be fired, sending its sound in all directions vertically and 

 obliquely down upon earth and sea. The first attempt to 

 realize this idea was made on July 18, 1876, at the firework 

 manufactory of the Messrs. Brock, at Nunhead. Eight 

 rockets were then fired, four being charged with 5 oz. 

 and four with 7| oz. of gun-cotton. They ascended to a 

 great height, and exploded with a very loud report in the 

 air. On July 27, the rockets were tried at Shoeburyness. 

 The most noteworthy result on this occasion was the hear- 

 ing of the sounds at the Mouse lighthouse, 8^ miles E. by 

 S., and at the Chapman lighthouse, 8 miles W. by N. ; 

 that is to say, at opposite sides of the firing point. It is 

 worthy to remark that, in the case of the Chapman light- 



