KEVIKW AND CONCLUSION. S61 



peat contained hamate o/'^/me, which was not affected by 

 tlio pure ainuionia, but in contact witli carbonate of am- 

 monia yielded carbonate of lime and huniate of ammonia. 

 In these cases the ammonia was la excess^ and the chemical 

 changes were therefore, in some particulars, unbke those 

 which occur when the humus preponderates. 



Brustlein, Liebig and others have observed that soils 

 ricli in organic matter (forest mold, decayed wood,) have 

 their absorptive power much enhanced by mixture with 

 carbonate of lime. 



Although Rautenberg has shown {Henneherg''s Journal 

 186, p. 439,) that silicate of lime is probably formed when 

 ordiaiary soils are mixed with carbonate of lime, it may 

 easily happen, in the case of soils containing humus, that 

 humate of lime is produced, which subsequently reacts 

 upon the alkali-hydrates or salts with which absorption 

 experiments are usually made. 



§ 6. 

 REVIEW AND CONCLUSION. 



The limits assigned to this work having been nearly 

 reached, and the more important facts belonging to the 

 present chapter brought under notice, with considerable 

 fulness, it remains to sum up and also to adduce a few 

 considerations which may appro2:>riately close the volume. 

 There ai-e indeed a number of topics connected with the 

 feeding of crops which have not been treated upon, such, 

 especially as come up in agricultural practice ; but these 

 find their place most naturally and properly in a discussion 

 of the improvement of the soil by tillage and fertilizers, 

 to which it is proposed to devote a third volume. 



What the Soil mast contain.— In order to feed crops, 

 16 



