On Agricultural Chemistry. 



11 



without manure. In the case of No. 9, indeed, the produce ex- 

 ceeds by li bushel that given by farm-yard manure, and in that 

 of No. 10 it is all but identical with it. And if we take the 

 weights of total corn, instead of the measure of the dressed corn, 

 to which latter we chiefly refer, merely as a standard more con- 

 ventionally understood. No. 10, by ammonia only, has given both 

 more corn and more straw than the farm-yard manure, with all 

 its minerals and carbonaceous substance. 



Let us see whether this almost specific effect of nitrogen, in 

 restoring, for the reproduction of corn, a corn-exhausted soil, is 

 borne out by the results of succeeding years. 



In relation to the third experimental year (harvest 1846), we 

 have already given in a tabular form in our former article most of 

 the results ; but for want of time and space the attention of the 

 reader was specially called to one or two of them only. We shall, 

 therefore, on this occasion offer a few remarks on some of those not 

 previously discussed; and we should have omitted all reference to 

 the results obtained with the wheat manure of Professor Liebig, 

 to which we have already called attention, had not the Professor, 

 in the new edition of his ' Letters,' whilst fully admitting the 

 failure of the manure — the composition of which, to use his own 

 words when commenting upon it, could be no secret, since every 

 plant showed by its ashes the due proportion of the constitu- 

 ents essential to its growth" (page 482), — not expressed any 

 doubt as to the principle involved in such a manure, but, on the 

 other hand, implied that the failure was due to a yet imperfect 

 knowledge of the mechanical form and chemical qualities required 

 to be given to the necessary constituents in order to fit them for 

 their reception and nutritive action on the plant, rather than to 

 any fallacy in the theory which v;ould recommend to practical 

 agriculture the supply by artificial means of the constituents of 

 the ashes of plants as manures. 



We do not mean to say that Liebig's manure was not at fault as 

 to its mechanical form and chemical qualities, and from their 

 failure the same might, perhaps, be said of all the mineral mix- 

 tures employed in our experiments. We must be careful, how- 

 ever, not to rely upon an argument of this kind without sufficient 

 ground, for it must be observed that in this way every negative 

 result of experiment whatever might be held as showing nothing, 

 and indeed that every positive one was equally little to be trusted ; 

 for it might be said that had we managed better, the one which is 

 now negative might have been the most successful, and thus ex- 

 periments of any kind would be at an end, and useless. 



But to return to the experiments. The following table gives 

 our selection of the results of the third season, 1846: — 



