ME. ABEL’S EESEAEOHES ON GUN-COTTON. 
243 
When the box was opened, the litmus paper was found to have assumed a pink tinge, 
and the usual faint odour of confined gun-cotton was somewhat more manifest than if 
the box had been preserved under ordinary atmospheric conditions, but the material 
itself was quite unchanged. 
c. Exposure of gun-cotton in different conditions to a heated atmosphere in a confined 
space. — A chamber was constructed of brickwork, and suitably fitted for the reception of 
a number of large ammunition-boxes. A system of iron pipes, standing in the centre of 
the chambers, was supplied with hot water from a boiler placed in a shed distinct from 
the chamber and heated with gas. By this arrangement, the atmosphere in the room 
could he maintained at artificial temperatures without risk of accident. 
The boxes in which the gun-cotton was packed were the large ammunition-cases 
employed in military service, and consisted of thin tinned-copper cases enclosed in stout 
wooden boxes and very tightly closed with double lids. Experience showed, some time 
after the experiment was set on foot, that the employment of these metal-lined cases 
was unquestionably prejudicial to the gun-cotton, as the very slightest development of 
acid in the latter, where it was in actual contact with the sides of the case, established 
oxidation of the metal surfaces, whereby in turn the alteration of the gun-cotton at those 
parts was considerably promoted. 
Each case was fitted with a central tube to receive a registering thermometer, in the 
same way as the black boxes already described. The gun-cotton was closely packed, and 
the description of material placed in the several boxes was varied (as shown in the fol- 
lowing Table) with the view of examining the effects of different modifications in the 
manufacture upon the power of gun-cotton to resist the effects of heat. 
In the first instance, the temperature of the hot-air chamber was raised as rapidly as 
possible to between 49° and 50°, and then maintained at that temperature (within narrow 
limits on either side) for several hours daily, periodical readings of a thermometer 
exposed in the room and of those enclosed in the central tubes of the boxes were 
recorded. The heating of the chamber was commenced at six in the morning; the 
maximum temperature was generally attained at about eleven o’clock, and it was 
maintained (for seven hours) until six in the afternoon. 
After the first day of the experiment the temperature of the air in the chamber at six 
in the morning was always from 8° to 11° lower than the temperatures recorded in the 
boxes, excepting on the Monday morning, when the difference amounted only to between 
1° and 3°. The rapidity with which the temperature rose in the interior of the boxes 
varied somewhat ; the thermometers were stationary, or fell slightly for about two hours 
after the heating was commenced ; at the close of that period the air in the chamber 
was generally (except on Mondays) 10° or 12° higher than that of the centre of the gun- 
cotton, the latter then rose gradually, almost reaching the maximum in ten hours, but 
still rising 2° or 3° in the last two hours. Even after seven hours’ exposure to ah’ at the 
maximum temperature, the contents of the case were, in the centre, from 5° to 9° cooler 
than the external air. The daily records of temperature obtained from the different 
