CHEMICAL HISTORY AND APPLIANCES OF GUN-COTTON. 
77 
fine yarn or thread, which are fitted compactly in layers, one over the other, upon a 
small cylinder or spindle of wood. In both of these arrangements the combustion of the 
charge can proceed only from the external surfaces towards the interior of the cartridge. 
On the other hand, the charges for shells, in which the most rapid explosion is most 
effective, and the priming for quick-matches which are intended for firing several 
charges simultaneously and almost immediately upon the application of flame, consist 
of cylindrical, hollow, and moderately compact plaits (similar to lamp-wicks), made of 
gun-cotton thread, or very fine yarn. These plaits are produced in pieces of any 
length, and when employed as quick-matches are compactly enclosed in cases of water¬ 
proof canvas or other similar materials. The charges to be used in mines, in which the 
most destructive effects are aimed at, consist of pieces of very firmly-twisted rope, with 
a hollow core along the centre, the number of strands of which it is composed varying 
with the size of the charge to be used. For quarrying and blasting purposes, small lengths 
of the rope are employed singly; for military operations (demolition of works, etc.), it is 
packed into moderately stout cases of sheet-metal. In these hollow ropes and plaits 
of gun-cotton, the flame produced by the burning of that portion to which heat is 
applied, penetrates at once to the interior and into the interstices of the charge, and 
hence the entire mass of gun-cotton is converted into gas and vapour, with almost 
instantaneous rapidity. A striking illustration of the very opposite effects which can 
be produced by very simple modifications in the mechanical arrangement of the gun¬ 
cotton is afforded by the following experiment:—If two or three strands of gun-cotton 
yarn be very loosely twisted together and inserted into a tube of glass, or other material, 
in which they fit so loosely as to be readily drawn backwards and forwards, upon apply¬ 
ing heat to a projecting portion at one end of the tube, the gun-cotton thus arranged 
will explode with great -violence, completely pulverizing the tube, if it be of glass; and 
the combustion will take place with such almost instantaneous rapidity that small por¬ 
tions of unburnt gun-cotton will actually be scattered by the explosion. But when, 
two or more strands of the same gun-cotton yarn are tightly twisted, singly in the first 
instance, then made up into a firm cord, solid throughout, and enclosed in a glass tube 
or some other description of case into which the cord fits very tightly, if a protruding 
end of the gun-cotton be then inflamed, the cord will bum with moderate rapidity 
until the fire reaches the opening of the case, when the combustion will pass over from 
the ordinary kind to a form which can only be described as a smouldering ; the lighted 
extremity of the gun-cotton simply glows within the case, while a steady jet of flame 
(furnished by the combustible gases evolved from the gun-cotton) continues to burn at 
the open extremity of the case until the contents of the latter are consumed, The 
gun-cotton not only burns extremely slowly under these conditions, but also with the 
greatest regularity, so that the rate of combustion of a given length of the enclosed 
cord may be accurately timed. The rapidity of combustion of gun-cotton arranged in 
this given form may be regulated by the number of strands in a cord, and the degree of 
their compactness ; and it is by this new modification of General von Lenk’s system of 
arranging gun-cotton that the lecturer has succeeded in applying this material to the 
production of slow-matches and time-fuzees; uses for which it had not previously been 
found suitable. 
Keference has just been made to inflammable gases evolved by gun-cotton while it 
undergoes a very slow combustion. The composition of gun-cotton renders it self-evi¬ 
dent that, under any circumstances, the explosion of this substance must be accom¬ 
panied by the production of a very considerable proportion of carbonic oxide. The 
large body of flame, always observed when gun-cotton is ignited under ordinary 
circumstances, is principally due to the combustion of carbonic oxide and, probably 
also, of small quantities of carbo-hydrogen compounds, which, together with minute 
suspended particles of the mineral matter contained in the gun-cotton, give to 
the flame its brightness. If a tuft of gun-cotton be ignited in a capacious and some¬ 
what deep vessel, the flame actually resulting from the burning of the tuft may be dis¬ 
tinctly seen surrounded by a large body of flame, produced by the burning gases, which 
continue apparent for a very appreciable time after the disappearance of the fl ish of 
flame furnished by the explosion of the gun-cotton. If similar tufts be ignited in at¬ 
mospheres of hydrogen, nitrogen, carbonic acid, coal-gas, etc., the combustion oi the 
gun-cotton is only accompanied by a very small and pale flame, of instantaneous dura¬ 
tion. Similarly, if gun-cotton be ignited in a vessel which has been previously ex- 
vol. yi. n 
