ABSORPTIVE POWER OF THE SOIL. 355 
Peters concludes the account of his valuable investiga- 
tion with the following words: “ Absorption is caused by 
the surface attraction which the particles of earth exert. 
In the absorption of bases from salts, a chemical trans- 
position with the ingredients of the soil is necessary, 
which is made possible through céoperation of the surface. 
attraction of the soil for the base.” (Vs. St., II, p. 151.) 
If we admit the soundness of this conclusion, we must 
also admit that in the soil the physical action is exerted 
in sufficient intensity to decompose salts, by the hydrated 
silicates alone. We must also allow that the displace- 
ments observed by Way and Eichhorn in silicates, are 
primarily due to mere physical action, though they have 
undeniably a chiefly chemical aspect. 
That the phenomena are modified and limited in certain 
respects by physical conditions, is to be expected. The 
facts that the quantity of solution compared with the 
amount of soil, the strength of the solution, and up to 
a certain point the time of contact, influence the degree 
of absorption, point unmistakably to purely physical in- 
fluences, analogous to those with whose action the chem- 
ist is familiar in his daily experience. 
Absorption of Acids,—It has been mentioned 
already that phosphoric and silicic acids are absorbed 
by soils. Absorption of phosphoric acid has been 
invariably observed. In case of silicic acid, excep- 
‘tions to the rule have been noticed. In very few in- 
stances has the absorption of sulphuric and nitric acids 
or chlorine, from their compounds, been remarked 
hitherto by those who have investigated the ab- 
sorbent power of the soil. The nearly universal con- 
clusion has been that these substances are not subject in 
any way, chemical or physical, to the attraction of the 
soil. Veelcker was the first to notice an absorption of 
sulphuric acid and chlorine. In his papers on “ Farm 
Yard Manure,” etc., (Jour. Roy. Ag. Soc., XVIIL, p. 140,) 
