320 Agricultural Chemistry. 



annually the quantity corresponding to one crop, the result would 

 probably have been very different. 



And, although Mr. Lawes observed that the small quantity of 

 my manure which he used, by simply increasing the proportion 

 of ammoniacal salt contained in it, and by the addition of rape- 

 cake, contributed to increase the produce of his fields, and this, 

 in the majority of cases, to a greater extent than he was able to 

 do by the use of his fanciful mixtures, with equal additions of 

 ammoniacal salts and rape-cake, he yet maintains that he has 

 proved, that the principle of the composition of my manure is 

 fallacious, and does not hold good in practice. 



The main question — that of the comparative permanence of 

 the increased produce, during a series of years, under the use of 

 manures prepared according to the results of analysis, and under 

 that of the mixtures imagined by him — has been entirely over- 

 looked by Mr. Lawes. He never thought of inquiring whether 

 the origin of the difference in the efficacy of these manures for 

 wheat, in relation to time, the excess of ammonia and rape-cake 

 being excluded, should not be sought for in their peculiar form 

 and quality. He thought that the facts observed by him proved 

 the fallacy of my theory, as if he had had any the most distant 

 idea of testing the truth of that theory. He made hundreds of 

 trials with his own mixtures, varied in every possible way. 

 Why, then, did he not make as many trials with mixtures pre- 

 pared on my principles, and varied in the same manner ? This 

 a man of science would certainly have done, before he condemned 

 my theory. 



If a kind Providence, in compassion to agriculture, were to send 

 down on our fields twice as much ammonia as is required for a 

 full crop of wheat, this would not be enough for Mr, Lawes. 

 Were he permitted to express his wishes in this matter, he would 

 address to Providence the request that to his fields and to his 

 mixtures a fivefold supply might be vouchsafed.* It is only then 

 that he can feel sure of obtainins: somethins; more than one-half 

 more than his fields, Avithout any supply of ammonia, produced. 

 Such views would be simply ridiculous, Avere they not so injurious 

 in their consequences. 



* " I am inclined to think that, for practical purposes, we may assume 5 lbs. of 

 ammonia to be required for the production of every bushel of wheat beyond the 

 naturaV yield of the soil and season" {^Journal, viii. p. 246). Again (p. 482), 

 " We do not intend to enter fully into the question of the accuracy of this estimate, 

 but we may observe, in passing, that among the plots, the history of which we 

 have given in the preceding pages, down to the last harvest, there is not one, even 

 under the best conditions as to (his, Mr. Lawes's) artificial mineral supply, where 

 the ammonia, on an average of seasons, has given an increase equal to 'our 

 estimate." 



