512 Learned Soctettes. 
have been principally founded, are to be ascribed to such 
variations in the nature of the material operated upon. 
Very numerous and extensive experiments and observa- 
tions have been carried on during the last four years at 
Woolwich, both with small and large quantities of gun- 
cotton, for the purpose of completely investigating the 
conditions by which the stability of this substance, when 
under the influence of light and heat, may be modified, and 
with the view to ascertain whether results recently arrived 
at in France apply to gun-cotton as manufactured in this 
country. The principal points which have been established 
by the results arrived at in these investigations may be 
summed up as follows :—1. Gun-cotton produced from 
properly purified cotton, according to the directions given 
by von Lenk, may be exposed to diffused daylight either 
in open air or in closed vessels for long periods without 
undergoing any change. The preservation of the material 
for three and a half years under those conditions has been 
perfect. 2. Long-continued exposure of the substance in 
a condition of ordinary dryness to strong daylight and sun- 
light, produces a very gradual change in gun-cotton of the 
description defined above ; and the statements which have 
been published regarding the very rapid decomposition of 
gun-cotton when exposed to sunlight do, therefore, not 
apply to the nearly pure trinitro-cellulose obtained by 
strictly following the system of manufacture now adopted. 
3. If gun-cotton in closed vessels is left for protracted 
periods exposed to strong daylight or sunlight in a moist 
or damp condition, it is affected to a somewhat greater 
extent; but even under these circumstances the change 
produced in the gun-cotton by several months’ exposure is 
of a very trifling nature. 4. Gun-cotton which is exposed 
to sunlight until a faint acid reaction has become developed, 
and is then immediately afterwards packed into boxes 
which are tightly closed, does not undergo any change 
during subsequent storage for long periods (the present 
experience on this head extends over three and a half 
years). 5. Gun-cotton prepared and purified according to 
the prescribed system, and stored in the ordinary dry con- 
dition, does not furnish any indication of alteration beyond 
the development, shortly after it is first packed, of a slight 
peculiar odour and the power of gradually imparting to 
litmus, when packed with it, a pink tinge. 6. The influence 
exercised upon the stability of gun-cotton of average 
quality, as obtained by strict adherence of von Lenk’s 
