322 L. Lesquereux on the Origin and Formation of Prairies. 
r. 
is objection, I think, is groundless. As we have seen, in 
considering the surface of the low and of the flat prairies, wher- 
ever the drainage is insensible, water can scarcely have any action 
in digging trenches. In the spring, or after heavy rains, its slow 
movements extend over the whole breadth of the low grounds, 
scarcely displacing or carrying away the finest material. This 
gr g the s 
marked by swells and deep furrows. In fact, the kuolls of the 
prairies are of quite a different form from the long continuous 
parallel undulations of the bottom of the seas. Moreover; 
