ME. ABEL’S EESEAECHES ON GUN-COTTON. 
213 
their openings oyer mercury and exhausted in the manner already described, so that the 
height of the mercury-column in these tubes, at the commencement of the experiments, 
was very nearly that of the barometer at the time. Sufficient gun-cotton was employed 
to till the globes pretty compactly. The bulbs were enclosed in metal water-baths, in 
which they were always perfectly surrounded by water maintained for definite daily 
periods at a constant temperature by gas-flames, accurately adjusted by self-acting regu- 
lators. Daily observations were made, before heat was again applied, of the height of 
mercury in the tube (with the necessary corrections), of the appearance of the gun-cotton 
through the glass, and of any other points worthy of note. 
Experiment 102. — 18 grms. of air-dry gun-cotton, manufactured at Waltham Abbey 
in 1863, were heated for six days, seven hours daily, to a temperature ranging between 
36° and 38° C. The column of mercury was not permanently affected to the slightest 
extent during this period. It was afterwards intended to maintain the temperature for 
a long period at 49°, but upon the second day of this treatment, the heat was acci- 
dentally raised to 55°, it was therefore afterwards maintained at that point for a con- 
siderable period. After the first day of this treatment, the column of mercury continued 
to fall daily, to an extent ranging between 8 and 16 millims., during nine days’ further 
exposure for six hours daily to 55°. For three subsequent days the column fell 18, 
20, and 18 millims. ; on the thirteenth day the fall amounted only to 11 millims. On 
the fourteenth day the temperature rose accidentally to 60°, and remained at that point 
about thirty minutes; on that day the fall of the mercury-column amounted to 23 mil- 
lims. The temperature was afterwards maintained at 55°, but the daily depression of 
mercury did not correspond with the observations made before the temperature had 
accidentally reached 60°; on three successive days it was 43 millims., 24 millims., and 
37 millims. It appeared from these results that the increase of temperature to 60° had 
established a greater tendency to change in the gun-cotton, which afterwards continued, 
although the temperature was reduced to 55°. 
After this exposure of the gun-cotton to heat, from six to seven hours daily, for twenty- 
four days, during seventeen of which the heat applied was 55°, and for a short time 60°, 
the specimen was removed from the globe. It had not altered in appearance, but was 
found to be strongly acid to test-paper; it had a peculiar pungent odour, the fibre 
had become tender, and its explosiveness had diminished somewhat. A portion of the 
specimen was washed thoroughly, first in distilled water and afterwards in slightly alka- 
line water, then dried and placed in a bottle, in which it has been exposed to diffused 
light for three years without undergoing further change. Nitrous acid vapours could 
not be distinguished in the globe or tube at any time during the experiment, but soon 
after the temperature was raised to 55°, a few small yellowish crystals of mercury-salt 
(mercurous nitrite) appeared upon the surface of mercury in the tube, and were added 
to a little as the experiment proceeded. 
Experiment 103. — 16 grms. of the sample of gun-cotton used in the preceding experi- 
ment, and 14 1 75 grms of another sample, w 7 ere exposed side by side, in one and the 
mdccclxvii. 2 Gr 
