352 ReviciDS. — Liehig'^a Organic Chemistry. 



weeds, or with a plant which does not abstract the potash enclosed 

 in it. Now many plants in the family of the leguminoste , are re- 

 markable on account of the small quantity of alkalies or salts in gen- 

 eral, which they contain; the Vicia faha (Windsor bean,) for ex- 

 ample, contains no free alkalies, and not one per cent, of the phos- 

 {)hates of lime and magnesia. (Einhof.) The bean of the Phaseo- 

 us Vulgaris (Kidney bean) contains only traces of salts. (Bracon- 

 not.) The stem of the Medicago saliva (Lucerne) contains only 

 0.83 per cent., that of the Ervum lens (Lentil) only 0.57 of phosphate 

 of lime with albumen. {Crome.) Buck-wheat dried in the sun yields 

 only 0.681 per cent, of ashes, of which 0.09 parts are soluble salts. 

 {Zennech.) These plants belong to those which are termed fallow- 

 crops, and the cause wherefore they do not exercise any injurious in- 

 fluence on corn which is cultivated immediately after them is, that 

 they do not extract the alkalies of the soil, and only a very small 

 quantity of phosphates. 



The process of manure is to replace in a soil all those sub- 

 stances of which it has been deprived. Of animal manures, 

 such as the faeces or excrements, the quantity of nutritive sub- 

 stances varies according to the habits and food of the animal. 

 The comparative value of each of these have been long known 

 to agriculturists; while their application has been made a 

 matter of great interest among those people who depend most- 

 ly on the products of the soil for support. Thus, in China, 

 whose agriculture presents a most surprising instance of in- 

 genuity and perseverance, with exuberant success, the most 

 careful and painstaking assiduity is employed in preserving 

 every such article of fertilizing power. Yet, important as 

 these substances seem, and as universal as this application is, 

 it is evident, from chemical analysis and experiment, that 

 other substances, containing their essential constituents, can 

 be substituted. 



In Flanders, the yearly loss of the necessary matters in the soil is 

 completely restored by covering the fields with ashes of wood or 

 bones, which may or may not have been lixiviated, and of which the 

 greatest part consists of phosphates of lime and magnesia. The 

 great importance of manuring with ashes has been long recognised 

 by agriculturists as the result of experience. So great a value, in- 

 deed, is attached to this material in the vicinity of Marburg, and in 

 the Wetterau, that it is transported as a manure from the distance of 

 eighteen or twenty-four miles. 



Bone manure possesses a still greater importance in this respect. 

 The primary sources from which the bones of animals are derived 

 are the hay, straw, or other substances which they take as food. 

 Now if we admit that bones contain fifty-five per cent, of the phos- 

 phates of lime and magnesia (Berzelius,) and that hay contains as 

 much of them as wheat-straw, it will follow that eight pounds of 



