PROPERTIES OF MANURES 247 



not only such manures as phosphates, nitrates, and 

 potash, but the minor constituents in the form of 

 soluble compounds. Many fruit trees are miserable 

 failures because the soil is incapable of properly 

 nourishing them. It is the law of minimum which 

 regulates the fertility of soils ; therefore, most soils 

 are improved by the addition of iron sulphate, magne- 

 sium sulphate, etc. Prof. A. Mtintz (of the 

 Ministfere de I'Agriculture de France) wrote the 

 author as follows : — " Je partage entiferement votre 

 mani^re de voir au sujet de la presence dans le sol 

 d'^l^ments autres que ceux qu'on est convenu 

 d'appeler exclusivement principes fertilisants. On 

 neglige beaucoup trop la recherche des formes 

 solubles de mati^res qui, quoique absorb^es en petite 

 quantity par les plantes, sont cependant utiles et 

 m§me indispensables. Le fer, le manganese, le 

 soufre, la magndsie doivent, h. mon avis, etre 

 regard^s comme des ^Mments fertilisants et lorsque 

 la terre ne les renferme pas en quantity suffisante 

 ou sous une forme accessible aux racines, la fertility 

 ne pent pas acqu^rir son maximum." , 



The subject of manuriag is one which can never 

 be exhausted, as there is always a vast field for 

 research, and there is much ground yet undis- 

 covered; but we can only work on "unresting," 



