246 THE CANADIAN NATURALIST. [Sept. 



wheat crops is by no means a slow process ; even if the 

 utmost allowance be made for the action of springs, and of 

 waters flowing from uncultivated lands, in bearing to the soil 

 minute quantities of phosphates, which might retard, although 

 they would be by no means sufficient to prevent a gradual 

 impoverishment. 



It becomes, therefore, absolutely necessary to follow the 

 principles laid down by Liebig,* and to restore to the soils the 

 cinereal elements of which they have been despoiled. Hence 

 the utility of farmyard and vegetable manures, as well as of 

 various products of the chemical manufactures applicable to 

 this necessary work of restoration. In no country, however, 

 can such a return of the valuable components of its soils be 

 sufficient to counterbalance the constant drain required 

 merely to furnish the elements of growth to its inhabitants : 

 for, if the utilization of sewage-matter and of every other 

 kind of organic residua were effected to the uttermost pos- 

 sible extent, — a condition very far from being realized, — 

 there would still always be a great unavoidable waste, by 

 which the essential constituents of the soils would, in process 

 of time, be sensibly diminished ; and, since there are but few 

 countries whose entire vegetable product is applied to the use 

 of the inhabitants, but that, on the contrary, a certain pro- 

 portion is almost always exported for the benefit of other 

 lands, there is usually a far greater deficiency than that re- 

 sulting from irrecoverable waste. This further loss is espe- 

 cially great to those newly peopled lands, whose rich virgin 

 soils have constituted them the granaries of the Old World. 



Thus a very large proportion of the vegetable produce of 

 North America, in the shape of cotton, wheat, sugar, and 

 tobacco, is employed in ministering to the necessities of 

 European countries ; and the result is a stupendous annual 

 withdrawal of their necessary constituents from all soils 

 occupied in satisfying these ever-increasing demands, and 

 this is especially true with regard to their limited quantities 

 of the salts of phosphoric acid. 



* Agricultural Lectures, Letters, etc., by Baron Liebig. 



