ABSORPTION OF HUMUS. 



toil, in sufficient quantity to form such soluble compounds with 

 mmic acid. 



Now, let us suppose that humic acid is absorbed by plants in 



the form of that salt which contains the largest proportion of 



lumic acid, namely, in the form of humate of lime ; and then, 



from the known quantity of the alkaline bases contained in the 



ishes of plants, let us calculate the amount of humic acid which 



might be assimilated in this manner. Let us admit, likewise, 



that potash, soda, and the oxides of iron and manganese have the 



same capacity of saturation as lime with respect to humic acid, 



md then we may take as the basis of our calculation the analysis 



•f M. Berthier, who found that 1000 lbs. of dry fir- wood yielded 



^•3 lbs. of ashes, and that in every 100 lbs. of these ashes, 



educting the chloride of potassium, the silicate, and sulphate 



f potash, 46-1 lbs. consisted of the basic metallic oxides, potash, 



coda, lime, magnesia, iron, and manganese. 



One Hessian acre* of woodland yields annually, according to 

 i >r. Heyer, on an average, 2650 lbs. of dry fir-wood, which con- 

 tains 10*07 lbs. of metallic oxides. 



Now, according to the estimates of Malaguti and Sprengel, 1 

 I j. of lime combines chemically with 10-9 lbs. of humic acid ,' 

 i 0*07 lbs. of the metallic oxides would accordingly introduce 

 i.ito the trees nearly 111 lbs. of humic acid, which, admitting 

 humic acid to contain 58 per cent, of carbon, would correspond 

 to 165 lbs. of dry wood. But we have seen that 2650 lbs. of 

 fir- wood are really produced. 



Again, if the quantity of humic acid which might be intro- 

 duced into wheat in the form of humates, is calculated from the 

 Known proportion of metallic oxides existing in wheat straw (the 

 sulphates and chlorides also contained in the ashes of the straw 

 not being included), it will be found that the wheat growing on 

 one Hessian acre would receive in that way 57£ lbs. of humic 

 acid, corresponding to 85 lbs. of woody fibre. But the extent 

 of land just mentioned produces, independently of the roots and 

 grain, 1780 lbs. of straw, the composition of which is the same 

 as that of woody fibre. 



* One Hessian acre is equal to 40,000 square feet, Hessian, or 26,910 

 •quare feet, English measure. 

 PART TI. 2* 



