42 YALE AGRICULTURAL LECTURES. 



SIXTH DAY. FEB. 7, 1860. 



Professor Joiixsox lias boldly set himself in array against a 

 new theory of Liebig's, for one thing, and scouts the utility of 

 soil-analysis, for another. Those who have read Liebig's recent 

 pamphlet on " Modern Agriculture," will remember his doc 

 trine that mineral matters are not in a soluble state in the soil ; 

 in support of which he quotes the experiment of passing 

 through a sample of fertile soil water holding in solution phos 

 phoric acid and other plant foods, and thereby removing the 

 salts entirely. The formerly soluble mineral matters he sup 

 poses to have been made insoluble in the passage through, and 

 putting this and that together, he says that if this be the case, 

 why then, plants must actually have the power of taking in the 

 insoluble material which they need for their growth, and mak 

 ing it soluble after it gets within their spongioles. Johnson 

 thinks Liebig's theory would be very pretty if the little if 

 were removed. In other words, he says that Liebig's experi 

 ment was rudely performed, and that the mineral matter was 

 not and never can be entirely removed from the water, and 

 hence Liebig's superstructural argument falls, like the Pember- 

 ton mills, for want of a sound basis. He says he knows of 

 beans and other plants having been grown and ripened in 

 naught but a watery solution of mineral and organic food a 

 fact which goes far towards proving that soluble matter is 

 used to full advantage by plants when they can get it. Al 

 though I do obeisance to Liebig, I think Johnson is right in 

 this instance, and so I fancy do many others. As to soil-an 

 alysis, Johnson reasons thus : One foot deep of the soil in an 

 acre weighs 2,000,000 pounds ; a crop of wheat will remove 

 say 200 pounds ; if that 200 pounds be not in an available state, 

 no crop will grow. To know if there be enough for the crop, 

 you take a little sample, say 100 or 1,000 grains, and analyse 

 it. Now, does any man living expect the chemist to tell, by 



