ABSUKPTIVJi: roWKU OF THE SVlL. 355 



Peters concludes the account of his valuable investiga- 

 tion with the following words : " Absorption is caused by 

 the surface attraction vhich the j)< articles of eurth esrert. 

 In the absorption of bases from salts^ a chemical trans- 

 position uith the ingredients of the soil is necessary, 

 which is m.ade possible through cooperation of the surface 

 attraction of the soil for the base:' (Ys. St., IT, p. 151.) 



If "we admit the soundness of tliis conclusion, Ave 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, thoiigh they have 

 imdeniably a chiefly cliemical 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 strengtli 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 baen 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 tlie 

 soil. Yoelcker was the first to notice an absorption of 

 sulphuric acid and chlorine. In his papers on " Farm 

 Yard Manure," etc., (Jour. Roy. Ag. Soc.,XYIII,,p. 140,) 



