S-46 Oji Paring and Burninj. 



silica, to US3 a manure which includes all the mineral elements 

 found in tlie ashes of the crop intended to be raised. In this 

 case the aljstract principle finds a strict application — hence a 

 corresponding' useful practical effect. But if a manure, composed 

 entirely of the ash-constituents of plants, is applied to clay soils, 

 and many other soils, containing an almost inexhaustible supply 

 of those very minerals which are added to it in the shape of a 

 mineral manure, it is plain that the same abstract truth can find 

 no application. The result of such misapplications of a correct 

 principle naturally must be what it has since proved to be in 

 numerous instances — a complete failure. But, as just mentioned, 

 the failure which has in many instances attended the application 

 of purely mineral manures does not sliow that mineral substances 

 are useless in relation to vegetable life, much less that organic 

 matters after all are more Important in relation to the growth of 

 plants than mineral substances. These mineral matters are 

 essential to the very existence of every kind of agricultural pro- 

 duce, and must, therefore, be present in the soil, or in the manure 

 applied to it, or else they will not grow ; organic food may be 

 altogether wanting in the soil or the manure, for under favourable 

 circumstances the plant can get it from the atmosphere. Thus 

 in a (Certain sense mineral matters are the more important. 



Whether it Is advisable to apply mineral or orf/anic food to the 

 soil, in cultivating certain crops on land of a particular descrip- 

 tion, is another and, as far as practice is concerned, an equally 

 imjiortant question. Here it may happen, and does happen, in 

 the ( ase of many soils, at least in England, that the artificial or 

 direct application of minerals (not the minerals themselves) is of 

 no use whatever. Speaking of the amplication of mineral matters 

 in such a case, most purely mineral manures may justly be con- 

 sidered to be unimportant, or at any rate of doubtful efficacy — 

 mucii less valuable than organic manures. But it cannot be said, 

 in a general way, that mineral matters are less important than 

 organic manuring elements, nor the reverse. 



It is evident at the same time that it is Impossible for prac- 

 tical men thoroughly to comprehend how far certain scientific 

 principles are applicable In a particular case if these principles 

 themselves are misunderstood ; nor can it lie expected that a 

 place will be secured for science in the affecthms of the prac- 

 tical man if the teachers of science be unacquainted, or but very 

 imperfectly Informed, on practical matters. Scientific men too 

 often fall into the grievous error of insisting upon the applica- 

 tion of abstract principles under all circumstances. 



Cliomical principles, though they may not always find a direct 

 application in agriculture, or though, wlien slated in the abstract, 

 they may require to be greatly modlfietl in practice, are, how- 



