194 
ME. ABEL’S BESEABCHES ON. GUN-COTTON. 
became dark brown, quite friable, and deprived of all explosive properties. When a 
considerably shorter time (about one hour) was occupied in the attainment of the maxi- 
mum temperature, the gun-cotton exploded on one or two occasions, but not until its 
temperature had reached 205° C. 
In the next experiments, the gun-cotton was employed in very small compact masses, 
and, resting upon a wooden support, was exposed to a continuously increasing tempe- 
rature. The passage from 15° C. to the explo ding-point ranged in these experiments 
from forty-five minutes to two hours. 
Temperature at commencement of Experiment =26° C. 
No. of experiment. 
8 
9 
10 
11 
12 
Time occupied. 
Forty-five minutes 
One hour twenty-five minutes 
One hour 
One hour 
Two hours 
Exploding-point. 
137°-5 C. 
136° „ 
137°*5 „ 
138°-5 „ 
138° „ 
Another series of experiments was instituted for ascertaining in what particular me- 
chanical condition the gun-cotton exploded most readily and at most uniform tempera- 
tures; and ultimately the material was employed in the form of pieces of loosely- 
twisted strand about 20 millims. long, and its exploding-point was determined by first 
raising the atmosphere of the air-bath to 105° C., then allowing the specimen to fall 
upon a diaphragm of wire gauze in the air-bath, at once increasing the temperature as 
rapidly as possible, and carefully reading the thermometer until the explosion occurred. 
The results of eight 'observations thus conducted were as follows : — 
No. of experiment. 
Exploding-point. 
13 
151°-5 C. 
14 
151° „ 
15 
151° „ 
16 
150°-5 „ 
17 
150°*5 „ 
18 
148°-5 „ 
19 
151° „ 
19a 
147° „ 
These last experiments, which appear the most trustworthy, indicate that the average 
temperature at which the gun-cotton explodes when in a condition most favourable to 
its rapid heating, is about 150° C. In two observations, in which the gun-cotton was 
in a very open condition, the temperature being raised more rapidly than usual, the ex- 
plosions occurred when the thermometer indicated 145° and 143°-5 C. ; and in the expe- 
riments preceding these, which were differently conducted, compact gun-cotton being 
exposed to heat for a considerable time, the point of ignition ranged between 136° and 
