204 FRAGMENTS OF 8C1ENC& 
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 Oollinson, 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- 
