ABSORPTION OF GASES. 71 



and gave that of other soils relatively. The diffi- 

 culty of working land is shown in the last column, 

 also by its adhesion to the plough. The relative 

 tenacity of different soils may be learned from the 

 preceding table (D). 



Absorption of oxygen^ carhonic acid, etc., from the 

 atmosphere. The power of the soil to absorb these 

 gases which are so important to vegetation, is de- 

 pendent, to a large degree, upon the state of division 

 of its particles. Baron Liebig maintains that the 

 property of absorbing fertility from rain-water is 

 dependent upon the amount of humus present in 

 the soil. We give his words : 



"Arable soil possesses in these respects the same 

 properties as charcoal. Diluted liquid manure, of 

 deep-brown color and strong smell, filtered through 

 the land, flows off colorless and inodorous; not 

 merely does it lose its smell and color, but the am- 

 monia, potash, and phosphoric acid which it holds 

 in solution are also more or less completely with- 

 drawn from it, and this in a far greater degree than 

 by charcoal. The rocks which by disintegration 

 give rise to soil, if reduced to fine powder, are just 

 as little possessed of this property as pounded coal. 

 There is no perceptible connection between the 

 composition of a soil and its power of absorbing 

 potash, ammonia, and phosphoric acid. Earth 

 abounding in clay with a small proportion of lime 



