CAUSES OF FERTILITY. 227 



the requisite supply would be obtained. The most fertile 

 soils contain alkalies in a suitable state to act, both upon the 

 vegetable matter, and to enter the vegetable organs, and 

 hence alkalies, especially potash and lime, are generally ben- 

 eficial to the soil. 



It will be seen, as a practical inference from what has been 

 stated, that alkalies may he added to the soil, as the quantity 

 needed is small. If it were required to add silica ; the task 

 of improving the soil would be utterly hopeless ; but a single 

 grain of lime or potash, in a hundred, is sufficient oftentimes 

 to ensure fertility, and it therefore appears, that alkalies as 

 well as vegetable matters are essential to a fertile soil. This 

 conclusion may be rendered still more evident, by the follow- 

 ing estimates of three fertile soils fi-om the farm of J. P. 

 Gushing, Esq. Watertown, Mass., in which the absolute 

 amount of the materials are stated, according to analysis, by 

 Dr. C. T. Jackson. The soil originated from granite, sie- 

 nite and greenstone. 

 Insoluble silicates per acre, A. B. C. 



six inches tillage depth 664.045 tons. 597.601 tons. 669.943 tons. 

 Alumina 

 Perox. of iron and mang. 



rtcJJ^, Phos. and create 'of lime 

 >k Soluable vegetable matter 



. k Insoluble do. 



'^^i Magnesia 

 Water 



Specific gravity 

 Cubic foot weighs 



By estinjates, like the above, it is obvious to any farmer, 

 that the salts and vegetable matter may be supplied to the 

 soil, and that the great object of improvement is to supply 

 them. 



It has been stated, that the mineral ingredients were of 

 far less consequence than it was formerly supposed. This is 

 true, yet it must not be inferred that they are of no impor- 

 tance at all. 



