AGRICULTURE. [CH. 



11. If soils so formed were allowed to remain 

 where they were first produced, we should find very 

 little difference between those soils and the rocks 

 from which they were formed, except so far as regards 

 their being in a more broken condition. But the 

 study of geology shows that great changes have taken 

 place on the surface of the globe, and that when soils 

 have thus been formed from rocks, they have fre- 

 quently been washed away and mixed with soils 

 produced from other rocks. Soils of this character 

 are often found in our valleys, and are distinguished 

 as alluvial soils. In many cases these mixed soils 

 have been again formed into rocks, and after long 

 periods of time, these rocks have again become con- 

 verted into soil. Animal and vegetable life have also 

 exerted very great influences upon the character of 

 many of these reconstructed rocks. Thus our soils 

 differ very much in character and composition, according 

 to the varying character of the rocks from which they 

 may have been produced, and also according as they 

 may have been more or less intermixed with other soils. 



12. There are some soils which are not produced by 

 these means, such as Peaty Soils. These consist 

 of vegetable matter which has grown and decayed, 

 generally in the place where these soils are found. 

 Their mode of production is peculiar. They are 

 generally found in places from which the water cannot 

 easily pass away. Here aquatic vegetation and mosses 

 establish themselves, and as they require a liberal 

 supply of water for their growth, they flourish luxuri- 

 antly. Growth after growth takes place, decaying 

 matter accumulates, which encourages further growth, 

 so that ultimately the rising bed of peat is held only 

 in check by the supply of water. When they have 

 grown up as high as the water allows them to grow, 

 tougher and more woody plants establish themselves; 

 these give the harder and firmer surface which is 

 found upon our peat bogs and mosses. 



