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Economical Geology of Massachusetts. 367 
of all successful cultivation. Its importance has been not so much overlooked as 
undervalued. Hence, on this point the least light has been reflected from the 
labors of Davy and Chaptal. It needs but a glance at any analysis of soils, pub- 
lished in the books, to see that fertility depends not on the proportion of the earthy 
Ingredients. Among the few facts, best established in chemical agriculture, are 
these ; that a soil, whose earthy part is composed wholly, or chiefly, of one earth ; 
or any soil, with excess of salts, is always barren; and that plants grow equally 
well in all soils, destitute of geine, up to the period of fructification,—failing of 
geine, the fruit fails, the plants die. Earths, and salts, and geine, constitute, then, 
all that is essential ; and soils will be fertile, in proportion as the last is mixed with 
the first. . The earths are the plates, the salts the seasoning, the geine the food of 
plants. The salts can be varied but very little in their proportions, without injury. 
The earths admit of wide variety in their nature and proportions. I would resolve 
all into ‘ granitic sand ;’ by which I mean the finely divided, almost impalpable 
mixture of the detritus of granite, gneiss, mica slate, sienite, and argillite; the 
last, giving by analysis, a compound very similar to the former. When we look 
at the analysis of vegetables, we find these inorganic principles constant constitu- 
ents—silica, lime, magnesia, oxide of iron, potash, soda, and sulphuric and phos- 
ave been overlooked from the known difficulty of detecting phosphoric acid. 
Phosphate of lime is so easily soluble when combined with mucilage or gelatine, 
that it is among the first principles of soils exhausted. Doubtless the good effects, 
the lasting effects, of bone manure, depend more on the phosphate of lime, than on 
its animal portion. Though the same plants growing in different soils are found to 
~ which it reposes. Modified they may be, to a certain extent, by peculiar form - 
ations; but all our granitic rocks afford, when decomposed, all those inorganic 
Principles which plants demand. This’is so true, that on this point the farmer al- 
Feady knows all that chemistry can teach him. Clay and sand, every one knows: 
soil too sandy, too clayey, may be modified by mixture, but the best possible 
Mixture does not give fertility. That depends on salts and geine. If these views 
are correct, the few properties of geine which I have mentioned, will lead us at 
once toa simple and accurate mode of analysing soils,—a mode, which determines 
®t once the value of a soil, from its quantity of soluble and insoluble vegetable 
nutriment,—a mode, requiring no array of apparatus, nor delicate experimental 
tact,—one, which the country gentleman may apply with very great accuracy ; and, 
With a little modification, perfectly within the reach of any man who can drive a 
team or hold a plough.” 
