Learned Socteties. 511 
of Professor A bel’s second memoir on Gun-cotton, delivered 
before the Royal Society :—The results of the many ob- 
servations which have been instituted prior to 1860 upon 
the behaviour of gun-cotton when exposed to diffused or 
strong daylight, or to heat, although they agree generally 
with those of the most recent investigations on the subject, 
as far as it relates to the nature of the products vbtained 
at different stages of its decomposition, cannot be regarded 
as having a direct bearing upon the question of the stability 
_of gun-cotton produced by strictly pursuing the system of 
manufacture prescribed by von Lenk, inasmuch as it has 
been shown that the products formerly experimented upon 
by different chemists varied very considerably in com- 
position. The investigations recently published by Pélouze 
and Maury (Comptes Rendus) into the composition of gun- 
cotton, and the influence exerted by light and heat upon its 
stability, are described as having been conducted with gun- 
cotton prepared according to von Lenk’s system; the 
general conclusion arrived at by those chemists with 
reference to the latter branch of the subject was to the 
effect that the material is susceptible of spontaneous decom- 
position, under conditions which may possibly be fulfilled 
in its storage and application to technical and warlike pur- 
poses, and the inference is drawn, partly from the results of 
earlier investigators, and partly from the exceptional 
behaviour of one or two specimens, that gun-cotton is liable 
to explode spontaneously at very low temperatures when 
stored in considerable quantities. It has been shown in my 
memoir of the Manufacture and Composition of Gun-cotton, 
published last year (Trans. Royal Society, 1866), that 
modifications in the process of conversion and purification, 
which appear at first sight of very trifling nature, exert 
most important influences upon the composition and purity 
of the product. Gun-cotton of quite exceptional character 
has been discovered in several instances, among samples 
received from Hirtenburg, and among the first supplies 
obtained from Stowmarket; other exceptional products 
have also been produced by purposely modifying, in several 
ways, the system of manufacture as pursued at Waltham 
Abbey. The very considerable difference exhibited between 
some of these and the ordinary products in their behaviour 
under equal conditions of exposure to heat and light, affords 
good grounds for the belief that the attainment of certain 
exceptional results, upon which the conclusions given in 
Pélouze and Maury’s report, condemnatory of gun-cotton, 
