ME. ABEL’S EESEAECHES ON GUN-COTTON. 
185 
(b) The investigation of the behaviour of gun-cotton upon exposure, under varied 
conditions, to artificial temperatures, and to such elevated natural temperatures as are 
occasionally experienced in particular localities ; 
(c) The examination of the influence exerted upon the stability of gun-cotton by 
special modes of preparing and preserving it. 
A few observations have been made upon specimens of gun-cotton which either were 
prepared by myself or came into my possession previous to the commencement of the 
present inquiry, but all actual experiments have been instituted with samples of products 
of manufacture obtained at Hirtenberg, Stowmarket, and Waltham Abbey, some modi- 
fications having been introduced, in special instances, in the ordinary system of opera- 
tion at the last-named manufactory, with the view to ascertain the nature and extent of 
their influence upon the stability of the product. 
Past I.— ACTION OF LIGHT UPON GUN-COTTON. 
The want of uniformity in power to resist the destructive action of light, exhibited by 
different specimens of gun-cotton with which chemists have experimented, has been 
additionally exemplified by the behaviour of numerous specimens of gun-cotton which 
have from time to time come into my hands or were prepared, by me, previous to 1862. 
I will limit my notice of such specimens to two examples. 
In the autumn of 1846 a small quantity (one or two pounds) of gun-cotton was pre- 
pared by me at the Royal College of Chemistry according to the directions which had been 
made public in Germany a short time previously. The product, which was insoluble 
in mixtures of ether and alcohol, was obtained by immersing carded and purified cotton- 
wool of very high quality for a few minutes in the prescribed mixture of nitric and 
sulphuric acids, afterwards exposing it for several hours to a current of water, then 
digesting it in a cold dilute solution of potassic carbonate, and finally washing it in pure 
water. The larger proportion of the product was gradually expended in lecture-expe- 
riments, but a specimen has been preserved by me up to the present time. For sixteen 
years it was simply enveloped in paper and kept in a. drawer much used ; at the expi- 
ration of that period, when it was found to be perfectly unchanged, not exhibiting the 
slightest acidity or odour, it was transferred to a stoppered bottle, in which it has been 
since exposed to diffused daylight for four years. This specimen still remains perfectly 
unchanged. 
Messrs. Hall of Faversham had the goodness, about three and a half years ago, to 
disinter at my request a sample of a large quantity of gun-cotton manufactured by them 
in 1847, and which they buried upon the occurrence of the disastrous explosion at their 
works in that year. This sample was much discoloured when received, but the fibre 
was strong, and the material did not appear to have undergone any change. Its explo- 
sive properties were, however, considerably inferior to those of gun-cotton prepared 
according to Sciionbein’s or Yon Lenk’s directions; and, upon analysis, it furnished 
