Region around Fort JVinnebago. 5 



The limestone which abounds about the surface, is subject to 

 rapid decomposition, and is often found passing into marl, which pro- 

 duces a luxuriant soil. On the other hand, it occasionally presents 

 the closeness of aggregation, and hardness of marble, and will receive 

 a fine polish. I have been credibly informed that marble of a supe- 

 rior quality is found at a place called Four Lakes, about forty miles 

 south of this place. 



Limestone is found in this district on the elevations, sufficiently 

 pure to make lime for architectural purposes. The only organic 

 remains that have been found in this rock to my knowledge, are 

 encrini, and indications of bivalve shells of some kind, the character 

 of which has disappeared. There are, however, some indications 

 of vegetable substances often observed in the indurated fragments; 

 they resemble the fern leaf. 



Among the elevations of this country, we often meet with exten- 

 sive prairies. The origin of prairies is doubtless attributable to the 

 extensive fires which scour the whole country when vegetable mat- 

 ter has become dry ; and I believe it is the prevailing opinion among 

 men of observation that this is the principal, if not the only cause. 

 We have constant evidence of the operation of this cause around us 

 the country is very thinly wooded, and it is still diminishing ; the 

 dry and decayed trees, are often felled to the ground by the flames, 

 and the most flourishing arrested in their progress. 



In this northern climate, the fires are more destructive perhaps, 

 than in the southern, because vegetation is of a shorter duration here, 

 yet prairies abound in the south west, resulting however from the 

 operation of nearly the same causes. 



in some instances, prairies are found stretching for miles around, 

 without a tree or shrub, so level as scarcely to present a single undu- 

 lation ; in others, those called " rolling prairies," appears in undula- 

 tion upon undulation, as far as the eye can reach, presenting a view 

 of peculiar sublimity, especially to the beholder for the first time. 

 It seems when in verdure, a real troubled ocean, wave upon wave, 

 rolls before you, ever varying, ever swelling ; even the breezes play 

 around to heighten the illusion ; so that here at near two thousand 

 miles from the ocean, we have a fac-simile of sublimity, which no 

 miniature imitation can approach. On many of the prairies, the soil 

 is equal, probably, to any in the world — vegetation is rapid and lux- 

 uriant ; yet they meet with any thing but cordial salutations from the 

 passing emigrant, who turns his anxious gaze, and bends his course 

 towards the nearest grove. 



