248 
MR. ABEL’S RESEARCHES ON GUN-COTTON. 
for about six weeks, when an explosion occurred, which destroyed the chamber and the 
whole of the samples, excepting some of the compressed gun-cotton. 
As is generally the case in accidents of this kind, the immediate cause of the explo- 
sion could not be traced with certainty. The usual periodical readings of the thermo- 
meters enclosed in the packages had been taken shortly before the explosion occurred, 
and all the temperatures last recorded were below that of the air in the chamber, which 
had been at 55°*5 from two till six o’clock ; not one of the packages had furnished any 
indication that heat was developed, but the temperature in the two small boxes was 
considerably higher than in the larger packages ; the comparatively small volume of 
gun-cotton became much more rapidly heated throughout, so that the temperature 
recorded in these instances at the close of the day’s heating was generally within 2° 
of the maximum external temperature. It appears most probable, therefore, that the 
small parcel of gun-cotton which had already suffered some change by exposure to 
heat, and which had since been exposed for six weeks to a heated atmosphere ranging 
between 54° and 55° - 5 for seven hours daily, eventually sustained further alteration, 
which, though very gradual for a time, at length increased to such an extent that heat 
was very rapidly developed, raising the gun-cotton to the temperature required for its 
explosion within a comparatively brief period. The experiments made at 100° C. with 
small quantities of gun-cotton which have been described in an early part of this paper 
(p. 197), demonstrated that, when once a considerable decomposition of the substance 
had set in, the development of heat was very rapid indeed. It was believed, how- 
ever, that the first establishment of decomposition would in all instances be indicated 
by so gradual a rise of temperature that frequent periodical observations of a thermo- 
meter placed in the centre of packages of heated gun-cotton would always afford the 
means of carrying on experiments of this class with security, a belief which was strongly 
supported by the results of the experiments carried on for periods of five, six, and ten 
months with the five large packages of gun-cotton. The power to resist serious decom- 
position upon continued exposure to a highly heated atmosphere had proved so unex- 
pectedly great in the case of every one of those experiments, that it was considered im- 
portant to ascertain, if possible, the full extent of those powers ; and hence, with what 
proved to be undue reliance upon the infallibility of the measures adopted to guard 
against accident, the experiments were protracted and the variety of the tests increased, 
far beyond the extreme limits necessary for the attainment of their original object, which 
was to ascertain how far gun-cotton, either of ordinary manufacture, or accidentally 
defective, or protected by special preparation, would resist change under conditions 
representing the extremes, both in extent and duration, of heat to which it might be 
exposed if stored, or used in active military service, in tropical climates. 
The Committee on Gun-cotton has endeavoured to collect reliable data with reference 
to the average and extreme temperatures to which gun-cotton might be exposed in ships’ 
magazines, during the passage of vessels through tropical regions, or to which it might 
be subject in India if directly exposed to the sun in ammunition-boxes; these being 
