ON THE APPLICATION OF GUN-COTTON TO WARLIKE PURPOSES. 13 
the maximum amount of moisture which the gun-cotton would absorb from a 
damp confined atmosphere. The great rapidity with which the specimens 
operated upon parted with the water absorbed, on exposure to the ordinary 
atmosphere, after the experiments had been proceeded with for some days, 
rendered the attainment of accurate numbers very difficult. The results, 
however, showed very definitely that no important increase in the amount 
of water absorbed took place when it had reached from 5:5 to 6 per cent. 
When these specimens had ceased to absorb moisture, they were, after the 
last weighing, exposed to the atmosphere at the ordinary temperature for 
one hour, and again weighed, when they were found to have parted with 
very nearly one-half of the total proportion of water absorbed. After 
further exposure to air for about four hours, the proportion of moisture re- 
tained had fallen to the average normal percentage (2 per cent.), and after- 
wards evinced no further tendency to decrease. 
Two specimens were kept confined as described, together with a vessel of 
water, for several weeks in a modcrately warm room. The water had then 
condensed, in numerous minute globules, upon the projecting filaments of the 
gun-cotton ; the specimens were therefore very highly charged with mois- 
ture. In this condition they were exposed to the air at the ordinary tem- 
perature ; within one hour and a half they contained only about 4:5 per 
cent. of moisture. After the lapse of a second similar period, the moisture 
had decreased to about 3 per cent. (3:16 in one specimen and 2:78 in the 
other). When again weighed, after a lapse of about four hours, the percen- 
tage of water had fallen, in both, to the average proportion, 
Experiments corresponding to the above were made with the specimen of 
gun-cotton referred to above as having been prepared from common cotton- 
wool. The rate of absorption of moisture of this specimen was found to be 
decidedly more rapid than that of the Austrian gun-cotton ; but they very 
closely resembled each other as regardedithe rapidity with which they again 
parted, spontaneously, with the moisture absorbed from a damp atmosphere, 
and the average proportion ultimately retained. The differences noted in the 
rate of absorption of moisture between the two varieties of gun-cotton, is 
most probably due to the difference in their mechanical condition. Some of 
the specimens of Austrian gun-cotton used in these experiments were picked 
asunder, as loosely as possible, instead of being exposed in the form of twists ; 
the difference thus established in the mechanical condition of the specimens 
did not affect, to any great extent, their relative hygroscopic properties. 
It was found impracticable, however, to reduce the gun-cotton rovings to the 
same mechanical condition as the gun-cotton prepared from finely carded 
wool, , 
It appears from the results above described, that— 
(a) The proportion of moisture absorbed and retained, under ordinary 
circumstances, by the gun-cotton, is about double that contained under similar 
conditions in good gunpowder (which averages one per cent.). 
(6) Gun-cotton possesses no tendency to absorb moisture beyond that’pro- 
portion, unless in very damp situations; and even under those circumstances 
the proportion of moisture absorbed is limited. Moreover its capacity for re- 
taining water (beyond the normal proportion) is so feeble that, however 
highly it may have accidentally become impregnated with moisture, it will 
return spontaneously to its original condition of dryness by simple exposure 
to the open air for a few hours. In these respects it possesses important 
advantages over gunpowder ; for although the latter contains, under normal 
conditions, less moisture than gun-cotton, it exhibits great tendency to absorb 
