810 EXTRACTS — NATURAL HISTORY. 
and fly as far as they are permitted : while the stool pigeon is tied to a narrow 
board, which, at the end, when the bird is fixed, rises and falls ; and both kinds 
of decoy, by flapping their wings, draw the attention of the passing flocks of wild 
pigeons, which are thus made to alight on prepared ground within reach of the 
concealed spring-net, or on a long pole rising a little from the horizontal line, 
so as to give the greatest eflFect to the discharge of the gun from the bush-house 
which conceals the sportsman. The net concealed by cut grass is sprung by a 
rope, which is pulled the moment after the pigeons alight upon the prepared 
ground. — SiUiman's Journal. 
Analysis of Gums. — M. Guerin has analysed several varieties of gums with 
the annexed results. Arabin, which constitutes the greater portion of g"uni 
arable, is composed of 
Carbon 43,81 
Oxygen 49,85 
Hydrogen 6,20 
Azote ,14 
.,^ 100,000 
. The Azote is considered non-essential. Gum arabic was found to consist of 
Arabin 79,40 
Water 17,60 
Ashes 3,00 
100,00 
Messrs. Gay-Lussac and Thenard found its composition to be 
Arabin 84,16 
Water 13,43 
Ashes 2,41 
100,00 
The difference of water found, depended upon the different methods of di-ying. 
The gum in this analysis was dried at 212 deg. in the air, while M. Guerin dried 
it at 257 deg. in vaccuo, which accounts for the larger quantity of water obtained 
by him. The quantity of ashes found by M. Guerin is the same as that procured 
by Vauquellin ; they consist of carbonate of potash, chloride of potassium, 
oxide of iron, allumina, silica, and magnesia. 
Gum Senegal. — 100 parts of this gum treated with 500 of nitric acid gave 
16,70 parts of mucic and oxalic acids. It is composed of 
Arabin 81,10 
.i3 Water 16,10 
Ashes 2,80 
100,00 
Its composition is therefore essentially the same as gum arabic. 
Mucilage of Linseed. — The soluble part of linseed is composed of 
Arabia and azotized matter 67,50 
Water 14,00 
Ashes , 18,50 
100,00 
