The Soil 13 



rent to be deposited elsewhere in the level bottom lands. 

 In every rock quarry a large part of this decomposed rock 

 must be removed to get at the solid rock below, and thus 

 more and more accumulation is made. After every hard 

 winter's frost a fresh accumulation can be found at the 

 base of the cHfifs, and the summer rains wash a fresh sur- 

 face for the winter to act upon. Thus the rivers eat into 

 the cliffs as the frost on the rock aids them. The result 

 is mineral soils for the lower country or deltas at the 

 mouth of the river. Even the summer rains have some 

 disintegrating power on the rocks, for the rain carries 

 with it the great decomposing agent of nature, carbon 

 dioxide. It has formed the calcium carbonate of the low 

 levels, the so-called limestone which was carried there by 

 water. Then when the rain falls on a vegetable soil the 

 water is impregnated with vegetable acids, which act read- 

 ily on Hmestone rocks and iron formations. In the great 

 swamps that line our Atlantic coast we find this process 

 of soil-making going on. The vegetable acids dissolve the 

 iron that plants have taken up, and bog iron ore is thus 

 deposited. This was utiHzed before the great accumula- 

 tions of iron ore were brought into use by the railroads. 

 Another force has acted on the land in 



The Influence ^j^^ formation of soil. This is the great sea 



of the Sea on . ,^ ^ . ,. , ^, 



the Land itself. In far distant ages the sea water 



was more dense with the carbonate of Hme 

 than now, and there were immense accumulations of 

 shellfish which used this lime in the construction of their 

 shells. These grew one generation upon the other, gradu- 

 ally burying the shells below till a deep deposit of Hme- 

 stone was formed from their remains. 



