BULLETIN OF THE BUSSEY INSTITUTION. 213 
lump of sugar is thrown into a glass of beer that has ceased to effer- 
vesce of itself, * so within the soil there must be a constant attraction 
of adhesion between the solid particles of earth and the excess of car- 
bonic acid in the solution of the acid carbonate of lime. 
On the other hand, Bineau has shown that dilute solutions of the 
acid carbonate of lime are capable of absorbing carbonic acid from 
the air more rapidly and abundantly than mere water can absorb the 
gas; and there can be no doubt that the strength of the solutions of 
the supercarbonate actually obtained from soils is determined by the 
fact that the absorptive power of a solution of carbonate of lime for 
more carbonic acid, which would tend to make the solutions strong, is 
balanced by the surface attraction of the soil itself for carbonic-acid 
gas, which would tend to make the solutions weak. Bineau has shown, 
moreover, that the intensity of the power by which carbonic acid 
dissolves carbonate of lime in presence of water is far from being in 
direct proportion with the quantity of gas dissolved. When the amount 
of the latter is elevated progressively, the increased solubility of the 
carbonate becomes less and less manifest, until at last it may no 
longer be perceived. By operating in the presence of large quantities 
of water, he was not able to retain dissolved by carbonic acid more 
than four-fifths the quantity of carbonate of lime necessary to make a 
bi-carbonate. 
I am inclined to believe that the decomposition of carbonic-acid 
water by the moist earths, in my experiments, is to be explained by a 
reference to the phenomena of adhesion above referred to; that is to 
say, that the decomposition is nothing more than a particular instance 
of the well-known surface action of solid substances upon carbonic- 
acid water, — the action, 1 mean, which is so familiarly and so well 
illustrated by throwing a bit of bread, or any other rough solid, into 
beer or other liquid charged with carbonic acid, that has been allowed 
to become flat by standing. In the cases where carbonic-acid water 
was made to pass through sharp sand, it would appear that the rapidity 
of the flow of the liquid through the sand was so great that only par- 
tial decomposition could occur. 
On comparing the foregoing results with some experiments of 
similar character, made in 1860 by the Dutch chemist, Van den 
* Compare Regnault in his “Cours Elémentaire de Chimie,” Paris, 2d 
ed. 1. 857, and Mulder “ Die Chemie der Ackerkrume,” Berlin, 1863, 2. 24. 
