IMPROVEMENT OF SOILS. 73 



This went on for some time, and the crops appeared 

 to be as abundant as ever. Then, after a number of 

 years, the people began to find that the crops in the 

 older fields, that had first been cleared, were not so 

 abundant as formerly. If a certain field near the first 

 settlements gave a hundred bushels of wheat when 

 the land was first used, it would now give only seventy- 

 five. That was still a good crop, and more wheat was 

 planted year by year. But the crops steadily grew less 

 and less, till finally there was not enough wheat pro- 

 duced in that field to pay for the seed and the labor 

 of cultivating it. There was more land a little farther 

 back in the woods ; and the settlers left the old fields, 

 and went deeper into the forest, cut down the trees, 

 and cleared more land. Again the virgin soil returned 

 bountiful harvests, and the farmers won more wealth 

 from the new ground. In a few years the new fields 

 refused to give these great harvests, and the settler 

 or his sons pushed on again farther west. This, in 

 time, became the agricultural history of our country. 

 The land was abundant and cheap ; and when the vir- 

 gin soils refused to give large crops, the farmers moved 

 on and on towards the west, in the search of fresh new 

 land. Whoever wanted large crops took new land ; 

 and, as there was plenty of it, the American people 

 grew rich at a wonderful pace. 



Here was certainly a curious matter. Why did not 

 the old soils keep on producing abundant crops ? The 

 plants did not consume the soil, and have nothing but 

 the bare rocks behind. The soil remained apparently 



