100 



CA11BONIFEKOUS 



LIMESTONES 



OP IOWA. 



ever, for a short distance, on the Upper Rapids of the Mississippi, charged with 

 Pecopteris (Table VI. Fig. 7), and other fossil plants. On these Rapids, near the head 

 of Smith's Island, the carboniferous rocks finally give place to Magnesian Lime- 

 stones of Upper Silurian date. 



CONCRETIONS IN CAEBONIFEK OUS SANDSTONE, MUSCATINE. 



SECTION V. 



THEIR PHYSICAL AND AGRICULTURAL CHARACTER. 



The carboniferous rocks of Iowa occupy a region of country, which, taken as a 

 whole, is one of the most fertile in the United States. No country can present to 

 the farmer greater facilities for subduing, in a short time, wild land. Its native 

 prairies are fields, almost ready made to his hands. Its rich, black soil, scarcely 

 less productive than that of the Cedar Valley, returns him reward for his labour a 

 hundred-fold. The only drawback to its productiveness is that, on some of the 

 higher grounds, the soil, partaking of the mixed character common to drift soils, is 

 occasionally gravelly ; and that, here and there, where the upper members of the; 

 coal-measures prevail, it becomes somewhat too siliceous. 



The rural beauty of this portion of Iowa can hardly be surpassed. Undulating 

 prairies, interspersed with open groves of timber, and watered with pebbly or rocky- 

 bedded streams, pure and transparent ; hills, of moderate height and gentle slope ; 

 here and there, especially towards the heads of the streams, small lakes, as clear as 

 the rivers, some skirted with timber, some with banks formed by the greensward 

 of the open prairie ; — these are the ordinary features of the pastoral landscape. 



For centuries, the sucessive natural crops of grass, untouched by the scythe, and 

 but very partially kept down by the pasturage of buffalo and other herbivorous 

 animals, have accumulated organic matter on the surface soil to such an extent, 

 that a long succession, even of exhausting crops, will not materially impoverish the 



