350 T. 8. Hunt— Chemical and Geological 
the soluble bases being in all cases removed by atmospheric 
waters in the form of carbonates. Such a decomposition of 
these silicates shows that the removal of silica in soluble form 
does not depend on the intervention of alkalies. 
The atmosphere of our earth at a pressure of 760 millimeters 
has a weight of 10,333 kilograms to the square meter, 0 
which the oxygen equals 2,376, and the carbonic dioxide (if 
we take Boussingault and Léwy’s determination of four and a 
half parts in 10,000 parts by weight) 4°64* kilograms. The 
alkali of 100 parts of orthoclase would require for its neutrali- 
zation 7°8 parts of carbonic dioxide, so that a cubic meter of 
this silicate, of specific gravity, 2°5, would, by the calculation of 
elmen, fix, in the process of decay, 195 kilograms of the 
gas, From this it results that a layer of orthoclase over the 
earth of 0°0238 meter, or one of less than 1:0 meter over 
one-fortieth of its surface, would, in its decomposition, absorb 
the whole amount of this gas now present in the atmosphere. 
Ebelmen further calculated that the formation of a layer of 
kaolin by this process, 500 meters in thickness, would require 
an amount of carbonic dioxide equal to many times the weight 
of the present atmosphere, 
_We have repeated and extended these calculations, with re- 
vised equivalent weights, and with the following results: A 
cubic meter of orthoclase, with a density of 2°5, and containing 
theoretically 16-9 per cent. of potash, equivalent to 7°89 0 
arbonic dioxide, would absorb in kaolinization 197°3 kilo- 
grams of this gas, while a cubic meter of albite of density 2°, 
containing 118 of soda, equivalent to 8:37 of carbonic dioxide, 
would require not less than 217°6 kifograms of the same. e 
figure of 195 kilograms, adopted by Ebelmen, was thus below 
the truth, and we may, in view of the considerable proportion 
of soda-feldspar in the oldest crystalline rocks, conveniently 
assume 200 kilograms as the amount of carbonic dioxide 
required to unite with the alkali from a cubic metre of ortho- 
clase or albite, and form therewith a neutral carbonate. 
* This, by an error in Ebelmen’s memoir, is given as only 1-24 kilograms. 
