MM. Pelouze and Maurey on Gun-cotton. 535 



mechanism leads us. There is but one serious exception known 

 to me to the law here indicated; this is copper, which MM. De 

 la Provostaye and Desains place higher than gold as a radiator, 

 though it is also higher as a conductor. When, however, the 

 immense change in radiative power which the slightest film of 

 oxide can produce, and the liability of heated copper to con- 

 tract such a film, are taken into account, the apparent exception 

 will not have too much weight ascribed to it. I have had a 

 cube of brass coated electrolytically with copper, silver, and 

 gold ; and, of all its faces, that coated with copper has the least 

 emissive power. This is probably due to some slight impurity 

 contracted by the silver. What we know of the deportment of 

 minerals also illustrates the law. Rock-salt 1 find to be a far 

 better conductor than glass, while MM. De la Provostaye and 

 Desains find the relative emissive powers of the two substances 

 to be as 17 to 6 : the radiant power of the salt is little more 

 than one-third that of the glass. So also with regard to alum : 

 as a conductor it is immensely behind rock-salt ; as a radiator it 

 is immensely in advance of it. 



Royal Institution, March 1864. 



LXIV. On Gun-cotton, with reference to the New Methods of 

 General Baron von Lenk for -preparing and employing this 

 Substance. By M. Pelouze, Member of the Institute, and 

 M. Maurey, Commissioner for Gunpowder*. 



I. Preparation of Gun-cotton in France and in Austria. 



A SHORT time after M. Schonbein's discovery of this new 

 explosive substance, its manufacture on a large scale was 

 commenced at the powder-mills of Bouchet. This establish- 

 ment, from 1847 to 1848, yielded about 5000 kilogs. for the 

 numerous experiments made in France with a view to substitute 

 this substance for gunpowder in mines and in fire-arms. 



The experiments made in Austria with the same object appear 

 to reach no further back than the year 1851 ; but they have 

 been pursued for a longer time than in other countries, thanks 

 to the perseverance of General Baron von Lenk, who was on the 

 first German Commission at Mainz, and who has continued to 

 occupy himself with the question. Up to 1862 the manufacture 

 of Austrian gun-cotton remained a mystery. "It is," says 

 Commandant d'Andlau, writing from Vienna on the 15th No- 

 vember 1861, " a secret which time alone will reveal." No stranger 



* Translated from the Annales de Chimie et de Physique for October 1864, 

 by Dr. E. Atkinson, Royal Military College, Sandhurst. 



