MAXIJAL OF AGRICULTUEE. 2 . 3 



carried away from the soil in quantity proportionate to the 

 analysis of the plant. Cows remove more inorganic matter 

 from the soil than fattening animals, from the fact of their milk 

 containing a considerable amount of such materials, not again 

 to be delivered to the soil. In like manner, young cattle, from 

 their requiring frame-building constituents, remove more than 

 does fattening stock. 



Phosphoric acid, then, and potash, especially the former, are 

 the most valuable of the soil's inorganic compounds, by reason 

 of their beinLi" the scarcest amono- them, but at the same time 

 requisite in considerable quantity for the health of cultivated 

 plants. The quantity of the remaining constituents is suffi- 

 ciently contained by most soils for ordinary requirements. 

 Potash is scarcest in light soils ; in the strong clay soils and 

 sundry closely related to several of the igneous rocks, it is con- 

 stantly present in the form of one of the silicates ; phosphoric 

 acid is also more abundant in the same class of soils. We saw, 

 that of the organic elements, that one least available to plant 

 life was nitrogen ; for all which reasons it is, that ammonia or 

 nitric acid, and phosphoric acid form the bases of all manufac- 

 tured manures ; ^vhich are called nitrogenous or phosphatic, 

 according to the nature of the basis prevailiDg. Before it was 

 commenced to manufacture mixtures of the necessary con- 

 stituents, they were principally derived for return to the soil 

 from the natural sources of farm-yard manure and town sweep- 

 ings and refuse. The farm-yard manure was applied to so much 

 of the ground as it could be spread over, the remaining arable or 

 cultivated land was bare fallovred for a season ; and, indeed, a 

 bare fallow, in certain respects, resembles a manuring, for besides 

 affording the opportunity of thoroughly cleansing the land from 

 weeds, the frequent ploughings and dressings it undergoes expose 

 its whole substance to the atmospheric action, which renders 

 such important chemical changes, and breaks up insoluble com- 

 pounds, iitting them for plant consumption in the next season. 



When the situation afforded facilities for the purpose, town 

 manure and other waste were turned to account. Put a demand 

 for other manures tlian these sprang up with the introduction of 

 turnip cultivation and generally im])roved farming. Guano was 

 imported, recourse was had to the use of bones ; and at length 

 the way was opened up to the production of artificial manures 

 suitable for all kinds of crops. And now the market is full of 

 manures compounded for the specific requirements of all our 

 cultivated varieties, and all manner of waste and all refuse, in 

 any respects ([ualilied to return plant-food to the soil, are well 

 economised, with the exception of town sewage, perhaps ; for 

 the many ditliculties preventing its profitable application to the 

 soil yet remain to be overcome. When we consider tlie fact of 

 our country not producing of itself sufficient food for the popu- 



