LAND AND WATER. 89 



pressed together when wet, it has the peculiar tendency 

 to form hard lumps, requiring considerable labor to 

 pulverize them and provide a fine seed-bed for crops. 



4. Peaty , or Mucky. This is one of the most valu- 

 able kinds of soil for agricultural purposes. It consists 

 of a mixture of ordinary soil with large quantities of 

 vegetable mold. It has great power to retain moisture 

 through periods of dry weather. It contains large sup- 

 plies of some kinds of plant food, which are gradually 

 converted into suitable form to meet the demands of 

 successive crops year after year. 



5. Limy, or Calcareous. Most soils contain some 

 lime. In some cases the quantity is so large as to give a 

 name to the soil. The variety of soil called marl con* 

 tains large quantities of carbonate of lime. 



The lime in soil serves to some extent as food for 

 plants, as all plants require a small quantity of it. It 

 also serves a good purpose indirectly, as a base, by com- 

 bining with acid substances in the soil, and forming salts 

 which are desirable as plant food. 



6. Loam. This is simply a general name applied to 

 ordinary soil, which contains a mixture of the varieties 

 mentioned, combined in varied proportions. If quite 

 sandy, it is called sandy loam ; if quite clayey, clayey 

 loam. 



QUESTIONS. 



What was the original condition of the earth ? How did the surface 

 become solid ? What is the present condition of the interior of 

 the earth ? How do we know it ? What caused the appearance of 

 water upon the earth ? How old is the earth ? 



How were the continents formed? Explain the origin of mountain 

 ranges and hills. Of what is soil largely composed ? How has it 

 been formed? Give the history of most of our present rocks. 



