THE HISTOKY OE EXPLOSIVE AGENTS. 
393 
method of storing gun-cotton in large quantities has been adopted by the Government, 
as tending to simplify very greatly the precautions needed in preserving large supplies 
of the material. 
Some experiments have been made with the object of determining as accurately as 
possible the minimum percentage of water which would deprive compressed gun-cotton 
of its power of inflaming when brought into contact with a red-hot body. Some disks 
which contained about 15 per cent, of water were exposed to air in a room where they 
parted very slowly with the water by natural evaporation. Their weight was deter- 
mined at the commencement of the experiment, and their power of inflaming was tested 
by pressing a red-hot iron rod in contact with one of their surfaces for a second or two, 
their weight being noted just before each trial. As a small proportion of the gun- 
cotton and water was vaporized each time the hot iron was applied, the weight of the 
disk was redetermined after each experiment. A period was at length reached at which 
the surface of the gun-cotton was inflamed, though not instantaneously, the flame 
spreading slowly from the point of contact with the source of heat, and being readily 
extinguished by a puff of breath. The proportion of water remaining in the disk when 
this point had been reached was 9 - 3 per cent. A disk which, though it smouldered 
slightly on the surface where the heated iron was applied, did not inflame, was found 
at that period to contain 10 ’7 per cent of water. 
When removed from the mould of the hydraulic press in which the finely divided 
gun-cotton or pulp has been converted into homogeneous and very compact masses 
(of about the density of water) by the application of a pressure of about six tons upon 
the square inch, the material contains about 15 per cent, of water. In this condition 
it may be thrown on to a fire or held in a flame without exhibiting any tendency to 
burn ; the material may be perforated by means of a red-hot iron, or with a drilling- 
tool, and the hard masses may with perfect safety be cut into slices by means of 
circular saws revolving with great rapidity. If placed upon a fire and allowed to 
remain there, a feeble and transparent flame passes over the surface from time to time 
as the exterior becomes sufliciently dry to inflame, and in this way a piece of compressed 
gun-cotton may be allowed to burn away very gradually indeed. In the same way a 
hank of gun-cotton yarn or a handful of the pulped material, which, after removal 
from the centrifugal wringing-machine used in the purifying operations, retains about 
20 per cent, of water, burns away very slowly if thrown upon a fire and allowed to 
remain there. Boxes in which the damp material was packed have been exposed singly 
to fierce fires until the box itself has been burnt through, but the gun-cotton has only 
been charred or has burned slowly wherever, and as soon as, it has become sufliciently 
dry upon the surface to be inflammable. When conducting the large-scale experiments 
on the burning of dry gun-cotton, it was considered desirable to institute a similar 
experiment with the moist material for the purpose of ascertaining whether its long- 
continued exposure to fire when closely packed might result in the development of 
conditions favourable to the explosion of some portion. 6 cwt. (672 lb.) of compressed 
MDCCCLXXIV. 3 F 
