ME. ABEL’S EESEAECHES ON GUN-COTTON. 
203 
The following are the principal facts demonstrated by the foregoing experiments : — 
1. The results furnished by the samples of Waltham Abbey gun-cotton demonstrate 
that different samples of the material, manufactured as far as possible in the same 
manner, are not alike affected by exposure for a fixed period to 100° C. under uniform 
conditions. Of thirteen samples of Waltham Abbey gun-cotton, four resisted in a 
remarkable manner the destructive effects of heat, and remained unchanged in physical 
properties and explosiveness after thirty hours’ exposure to 100° C. This treatment only 
developed acid to a slight extent in these particular samples ; but in the other nine spe- 
cimens it produced somewhat greater alteration nitrous acid was disengaged in more 
considerable proportions,- the fibre of the gun-cotton was rendered more or less rotten, 
and its explosiveness was diminished in different degrees. 
2. The comparative celerity with which nitrous acid is disengaged from different spe- 
cimens of gun-cotton upon exposure to 100° C., does not afford a reliable indication of 
their relative susceptibility to rapid decomposition at that temperature. As illustrations 
of this the following instances may be selected from among those furnished by the 
results detailed in the preceding Table. Those specimens of Waltham Abbey gun- 
cotton which exhibited uniform powers of resisting the destructive effect of heat (expe- 
riments 41, 45, 47, and 52), furnished the first faint indications of development of acid 
vapours at one hour, four hours, and fourteen hours, respectively, after first exposure to 
100° C. Three samples (experiments 44, 48, 49) which were altered alike, and 
slightly, by uniform exposure to 100° for thirty hours, exhibited the first symptoms 
of decomposition at l h 20 m , 2 h 30 m , and four hours after commencement of the experi- 
ment. Again, a sample which exhibited no sign of change beyond slight acidity at the 
close of the experiment (experiment 52) afforded faint indications of the development 
of acid in one hour, while another specimen which sustained comparatively considerable 
change (experiment 48) did not evolve any acid vapour until four hours after its first 
exposure to heat. An inspection of the results obtained with Stowmarket gun-cotton 
shows that, out of thirteen samples, five did not furnish signs of disengagement of acid 
vapours until after the lapse of five hours and upwards, while among the thirteen 
Waltham Abbey samples only three furnished no signs of change for four hours and 
upwards. On the other hand, these samples of Waltham Abbey gun-cotton were, after 
thirty hours’ exposure, only very slightly affected, while the Stowmarket samples just 
referred to, all exhibited important signs of change. Two samples from Stowmarket 
(experiments 54 and 60), though they evolved acid vapours within forty-five minutes of 
their first exposure, were not very greatly changed by the thirty hours’ treatment, while 
other two samples (experiments 62 and 64), which evolved no acid for five hours and 
5 h 45 m , were completely decomposed by the close of the experiment. 
A careful examination into the possible causes of these differences showed that they 
were to be ascribed, at any rate in very great measure, to variations in the proportion 
and character of the mineral matters contained in the specimens. Some few of the 
Waltham Abbey samples contained larger proportions of calcic and magnesian carbonates 
