148 Royal Society : — 



quality, such as is used in gun-cotton-manufacture, is, as might have 

 been anticipated, below the result obtained, under similar conditions, 

 with cotton of finer quality and more thoroughly purified. The 

 highest numbers obtained by treatment of such cotton, in small 

 quantities, with a considerable excess of acid, were somewhat below 

 181, from 100 of cotton. The increase of weight which this quality 

 of cotton sustains is, however, more generally about 78 per cent. 



Experiments are quoted which show that the attainment of lower 

 results with cotton of ordinary quality is ascribable to the existence 

 of higher proportions of foreign matters in the cotton under treatment. 



Some quantitative manufacturing experiments yielded results con- 

 siderably below those obtained with some of the same cotton in 

 laboratory operations (171 and 176 of gun-cotton having been pro- 

 duced from 100 of cotton). The causes of these differences are inves- 

 tigated and explained. 



The identity in their characters, and close resemblance in composi- 

 tion, of the most perfect results of laboratory experiments, and of 

 the purified products of manufacture, the close approximation fre- 

 quently exhibited by the weight of the former to the theoretical 

 demands of the formula € 6 H 7 N 3 O n (which may be expressed as 



<3 «{3NO 2 } G - ore " H >A.3N 2 5 ) ) 



and the satisfactory manner in which the unavoidable production of 

 somewhat lower results in the manufacturing operations admits of 

 practical demonstration, appear to afford conclusive evidence of the 

 correctness of either of the above formulae, as representing the com- 

 position of the most explosive gun-cotton, and demonstrate satisfac- 

 torily that the material, prepared strictly according to the system of 

 manufacture perfected by Yon Lenk consists uniformly of the sub- 

 stance now generally known as trinitro-cellulose, in a nearly pure 

 condition. 



April 26.™ J. P. Gassiot, Esq., Vice-President, in the Chair. 



The following communication was read : — 



" Experimental Researches in Magnetism and Electricity;"— Part I 

 By H. Wilde, Esq. 



This paper is divided into two sections, — the first being on some 

 new and paradoxical phenomena in electro-magnetic induction, and its 

 relation to the principle of the conservation of physical force ; the 

 second on a new and powerful generator of dynamic electricity. 



The author defines the principle of the conservation of force to 

 be the definite quantitative relation existing between all phenomena 

 whatsoever ; and in the particular application of the principle to 

 the advancement of physical science and the mechanical arts, certain 

 problems are pointed out which, in their solution, bring out results 

 as surprising as they are paradoxical. Although, when rightly inter- 

 preted, the results obtained are in strict accordance with the prin- 

 ciple of conservation, yet they are, at the same time, contrary to 

 the inferences which are generally drawn from analogical reason- 



