SOILS 



35 



does not leave along its course it carries out to sea 

 to help build the sand bars and mud flats there. 

 The rain drops have now gotten back to the beach 

 where they take up again the work of grinding the 

 soil. 



The work of moving water can be seen in almost 

 any road or cultivated field during or just after a 

 rain, and particularly on the hillsides, where often 

 the soil is loosened and carried from higher to 

 lower parts, making barren sand and clay banks of 

 fertile hillsides and destroying the fertility of the 

 bottom lands below. 



We have already noticed the work of freezing 

 water in splitting small and large fragments from 

 the rocks. Water moving over the surface of the 

 earth in a solid form, or ice, was at an earlier period 

 in the history of the earth one of the most power- 

 ful agencies in soil formation. Away up in Green- 

 land and on the northern border of this continent 

 the temperature is so low that most if not all of 

 the moisture that falls on the earth falls as snow. 

 This snow has piled up until it has become very 

 deep and very heavy. The great weight has packed 

 the bottom of this great snow bank to ice. On the 

 mountains where the land was not level the masses 

 of snow and ice, centuries ago, began to slide down 

 the slopes and finally formed great rivers of solid 

 water or moving ice. 



The geologists tell us that at one time a great 

 river of ice extended from the Arctic region as far 

 south as central Pennsylvania and from New Eng- 



