THE RELATIONS OF GEOLOGY TO AGRICULTURE. 551 



sition is gradual; but it would seem as if the constant destruction of 

 granites, by hammers and fires, would, in the course of years, tend to 

 remove unsightly rocks, and to improve the soil. 



Several varieties of soil occur in the granitic region. High up many 

 of the mountains the granites are bare, and allow little place for the 

 accumulation of organic matter. When the valleys are wide, the better 



Fig. 66 FRANCONIA MOUNTAINS, FROM CAMPTON, PEMIGEWASSET RIVER IN 

 THE FOREGROUND. 



part of the rock and other substances accumulate, as in Fig. 66; so that 

 after a while many farmers find they can allow their hills to revert to 

 timber, and cultivate the original bogs and swamps with better success. 

 Again, the soil is mixed, in consequence of the abundance of diverse 

 drift material. This is generally an improvement. Another variety is 

 found in the sandy plains of Carroll county, and the high terraces along 

 the Merrimack. The current of ancient times was just strong enough 

 to wash away the coarser particles into deposits by themselves, leaving 

 the finer particles to form clays. An instance of this segregation is seen 

 at Hooksett, where this clay is used for bricks, while the sand is accu- 

 mulated in piles by itself. 



