52 QUARTERLY JOURNAL. 



the only use of air and water is to aid in reducing the soil to the 

 state of extreme division. Others have said that the vegetable 

 matter in the soil was the great source of fertility, and till the 

 light of analytical science w'as thrown upon the subject, every 

 thing relating to it was vague and uncertain. It may now be 

 considered as settled that plants are dependent upon the earth, the 

 air, and water, for sustenance, and that deprived of either they 

 cease to exist. The earth furnishes the mineral ingredients with- 

 out which the plant could no more flourish than without those it 

 derives from water and the atmosphere. 



But in order to obtain a full comprehension of the action of ma- 

 nures and their individual value, it is necessary to take a more 

 particular view of the relation which plants sustain to the earth on 

 which they grow. That physician would be deservedly exposed 

 to ridicule, who, ignorant of nature and character of disease and 

 of the operation of medicines, should attempt to cure his patient 

 by administering a potion consisting of numerous ingredients, ho- 

 ping some one in the compound might reach the case. So ought 

 the farmer to be placed by his side, who remains ignorant of the 

 nature of soils and plants, and the action of manures, and applies 

 2l fertilizer^ as he terms it, composed in a similar manner, in the ex- 

 pectation that his crop will have the sagacity to select what it 

 needs 'and reject what it does not need. Such is not rational, 

 neither is it economical farming. The object of the farmer ought 

 to be to get the greatest yield from the least outlay — to apply those 

 manures which will supply the wants of the crop, and at the same 

 time render the soil permanently productive. We say this cannot 

 be done without knowledge, and that, not a general knowledge 

 that manures must be applied, but a particular and minute under- 

 standing of what constitutes a fertile soil, and what plants need to 

 develop their! powers in the greatest perfection. A full investi- 

 gation of these subjects would far exceed the bounds of an article 

 or even a series of articles in this Journal. The reader is referred 

 to the various standard works on agriculture, for a full discussion 

 of these points, and particularly to the lectures of Prof. Johnston, 

 which is in our estimation the best work of the kind yet printed. 

 In the meantime let us proceed as far as our limits will allow, and 

 as essentially introductory to the consideration of individual ma- 

 nures, to examine the relations of plants to the soil. 



