MANURES. 



83 



salts of potash in the manure applied to the land into compounds, 

 which, though not altogether insoluble in water, are yet suflS- 

 cientlj difficult of solution to permit only a limited and fixed quan- 

 tity to enter into the vegetable organism in a given period. The 

 case is difierent with salts of soda ; for as soils do not appear to 

 retain them in any high degree, and plants have no selecting pow- 

 er, but appear to absorb by endosmosis whatever is presented to 

 the spongioles of their roots in a state of perfect solution, it is 

 evident that more soda will enter into the plants when grown on a 

 soil naturally abounding in this alkali or heavily dressed with com- 

 mon salt, than when grown upon a soil poorer in soda. 



We have here at the same time an interesting illustration of the 

 fact that the soil is the great workshop in which food is prepared 

 for plants, and that we can only then hope to attain unto a more 

 perfect knowledge of the nutrition of plants, and the best means of 

 administering to their special wants, when we shall have studied, 

 in all their details, the remarkable changes which we know, through 

 the investigations of Mr. Thompson and Professor Way, take place 

 in soils when manuring substances are brought into contact with 

 them. The subject is full of practical interest, but also surrounded 

 by great difficulties, which, it appears to me, can only be overcome 

 when the investigation is taken up in a truly scientific spirit, with- 

 out reference to the direct application which, in due course, no 

 doubt, well established chemical principles will receive in agricul- 

 ture. It is the undue anxiety to obtain at once what is" properly 

 called a practical result — the grasping after results which may at 

 once be translated into so many bushels of corn — which is a great 

 hindrance to the more rapid advancement of agricultural science ; 

 and it is to be hoped, for the sake of the true interests of the really 

 practical man, that the voice of those capable of understanding and 

 appreciating purely scientific results, will be sufficiently powerful 

 to keep in check the too great anxiety for immediate results. 



In the next place, I beg to direct attention to the absorption by 

 the soil of the phosphates contained in drainings. If it is borne iu 

 mind that the soil and subsoil with which the liquid was brought 

 into contact, contained a large excess of carbonate of lime, it is 

 not more than would naturally be expected, if we should see the 

 soluble phosphates of the original drainings converted by the car- 

 bonate of lime into insoluble compounds. 



Having already remarked upon the power of this soil to retain 



