these fairy-rings is due to the large quantity of phosphated alkali, mag- 
nesia, &c., secreted by these fungi; and, whilst they are extending 
themselves in search of the additional food which they require, they 
leave, on decaying, a most abundant crop of nutriment for the grass. 
11, Gun-Cotton.—The results of the deflagration of gun-cotton 
have been determined as follows by Messrs. Porrett and TEscHe- 
MACHER, as stated by them ina paper read before the Chemical Society, 
on Dec. 6, (Pharm. Times, Dec. 19, 1846. 
52°53 grains of gun-cotton gave 100 cubic inches of gas, constituted 
as follows : 
Relative volumes. Cubic inches. Grains. 
2 14-286 
Carbonic acid, 7157 
yanogen, 1 7143 3°965 
Nitric oxyd, 5 35°715 11-478 
Carbonic oxyd, 5 35°715 10-714 
itrogen, 1 7°:148—100 2°184—35:070 
One hundred grains of the gun-cotton would consequently afford 
‘590 grains of the mixed gases. The other ingredients obtained 
from the same quantity were, water 20 grains, carbon 5, and oxalic 
acid 8-125, 
Since the printing of the account of gun-cotton on page 259, we 
have received a notice of the session of the Academy of Sciences of 
Paris for January 4, (L’Institut, No. 679,) containing the later investiga- 
tions of M. Petovze. His analyses have been numerous, and constant in 
Pelouze states that the results of the detonation of pyroxyline may 
be Tepresented as follows :-— ‘ 
46 volumes of carbonic oxyd, + = C? i 
2 volumes of carbonic acid, ° ~— co 
10 volumes of nitrogen, - . 
; 34 volumes of vapor of water, - = 17HO 
besides the SHO in the combination. These numbers, he adds, may 
