THE SOIL 41 



waves of the ocean dash upon them and grind them into sand. Rains, by 

 imperceptible degrees, dissolve them. Water gets into the cracks and by 

 freezing, forces off particles large or small. It is, therefore, by this weather- 

 ing process that the materials for our soils have been formed, and then 

 washed down from the higher to lower elevations, and spread abroad over 

 the rocky base. 



Many soils are formed from the gradual decay of the rocks on which 

 they rest, and are, therefore, of the same composition as the rocks themselves. 

 Other soils have no connection with the rocks beneath them, but are formed 

 by the decomposition of other rocks, mixed with decayed organic matter, and 

 brought down in flood and deposited on the low lands, making what are 

 known as alluvial soils. Then, too, in many instances the valley lands, 

 known as limestone soils, are the beds of ancient lakes, in which the lime- 

 stone was formed from the shells of mollusks ; the alluvial soil was afterwards 

 accumulated above the rocks, and the soil really contains less lime than soil 

 of a very different formation. 



The mountains of the present day are far lower than they were when first 

 formed, and the constant wearing away is still going on; the streams still 

 bring down from the mountains vast amounts of fresh soil to accumulate on 

 the flats and river bottoms, gradually forming more alluvium. 



Every hill that is in cultivation is constantly being carried off to the 

 lower lands ; hence, the low lands are of varying nature, sandy, clayey or silty, 

 according to the kind of material brought down to them from time to time. 

 Of course, there is a great variation in the mineral constituents of soils every- 

 where, depending on the chemical make up 1 of the rocks from which these 

 mineral matters come. Low lands about the bases of the hills are generally 

 fertile, not only because of the masses of soil transported to them in floods, 

 but because the rain water running down to them from the hills carries the 

 most soluble elements of fertility with it, to be absorbed by the low-land soil. 

 The low lands are constantly being extended and elevated, and the ponds are 

 constantly being filled, till finally the smaller lakes become fast land, being 

 filled up by. soil washed down from the hills and with the remains of the 

 vegetation they produce themselves. 



But while all the soft earth above the solid rocks is called soil, the soil 

 that the farmer is mainly concerned with is that upper portion that has be- 

 come altered by exposure to the effects of the air and the carbonic acid in the 

 rain water, and which has become mixed with the decay of vegetable mat- 

 ter and has assumed a darker color by reason of this vegetable decay. We call 

 this the soil, and all that lies below is called the subsoil. They may be, and 

 generally in our upland soils are, identical in their composition ; and differ 



