242 
ME. ABEL’S EESEAKCHES ON GUN-COTTON. 
magazine. After the lapse of If year it was examined, and its contents were found 
unchanged, except that the odour was decidedly less pungent than before. 
The data furnished by this preliminary experiment appeared to warrant the conclusion 
that further and more extensive trials of the effects of heat upon gun-cotton might be 
safely instituted. The following experiments were therefore made. 
b. Exposure of a large case of gun-cotton to the sums rays . — A large wooden box with 
blackened exterior, and fitted with a central tube to receive the recording thermometer, 
was compactly filled with rather more than 36 lbs. of gun-cotton, not silicated, which 
had been manufactured two years previously. This box was exposed to the open air on 
all bright sunny days between the middle of April and 1st of October last year; it was 
placed at a short distance from the brick wall of a hot-air chamber, in a position where 
it would be exposed to the maximum available amount of sunlight. At night and 
during wet weather it was placed under shelter. Headings were taken every two hours 
of the thermometer in the central tube, and of one exposed upon the outside of the box. 
The extreme temperature attained by the centre of the gun-cotton was 35°, the thermo- 
meter upon the box having indicated 49° on that day. Upon several occasions the 
thermometer in the centre of the box recorded 32° - 5. The latter generally attained its 
maximum temperature from four to six hours after the highest external temperature 
had been registered. The following are some of the highest readings recorded during 
the 5^ months’ exposure of the box. 
Inside the box. Outside the box. 
April . . . 18-5 27-5 
20 27-5 
21- 5 30-5 
26-5 40 
May .... 19 27 
20 35-5 
22- 5 37-5 
20-5 29 
29 44 
26-5 39 
25 42-5 
June ... 20-5 43-5 
20-5 43-5 
19-5 27-5 
26-5 36-5 
32-5 46-5 
25-5 34-5 
25 37 
33 47-5 
Inside the box. Outside the box. 
July .... 26-5 32-5 
35 49 
31-5 40*5 
31- 5 40 
25- 5 37 
32- 5 45 
26- 5 36 
28-5 43 
August . . . . 22-5 40-5 
24 39*5 
.22-6 39 
22-5 43-5 
24 41 
23 30-5 
23 36-5 
September . . 16-5-27 20-31 
