202 APPENDIX. 



thai formerly the sea covered this whole valley, from the 

 Gulf to Hudson's Bay, dividing North America into two con 

 tinents, of one of which the Alleghany, of the other the 

 Rocky mountain range formed the nuclei. This would seem 

 to be at a very remote period, as there are indications that it 

 has been inhabited at an antediluvian period. Pieces of 

 pottery have been found in different places, more than fifty 

 feet below the surface, in digging wells : and this position 

 can hardly be accounted for, without supposing a great dis- 

 turbance of the upper strata of the earth, and also a con- 

 siderable lapse of time. There is a very abundant deposit 

 of coal in several portions of the valley : beside the large 

 Illinois coal field : generally regarded as evidence of an ante- 

 diluvian vegetation. According to Mr. Guion, there are 

 large beds of coal on the Des Moines. The erratic deposits 

 are found upon the surface upon very distant points in this 

 region. They are mentioned by Nicollet upon the Tchan- 

 sansan and Tchankasndata, as well as high upon the St. 

 Peter's , and the author has observed them upon the Wabe- 

 sipinicon. Mr. Schoolcraft says the rock on the southern 

 shore of Lake Superior consists of granite, slate, and sand- 

 stone. 



The country bordering on the Missisippi, within the inha- 

 bited portions of Iowa, and below, is chiefly a mountain 

 limestone. In some localities, as already mentioned, are 

 strata of fossil cretaceous formation, composed mostly or 

 wholly of shell. At the top of the bluff at Burlington, at 

 about 150 or 200 feet above the mark of high water at the 

 usual stage of the river, covered only w^th a thin layer of 

 chert and vegetable mould of a few inches, is an encrinitic 

 limestone which may, from appearance, be altogether of this 

 shell. And, at Iowa City, the same shell composes a very 

 soft, fine-grained marble of a dingy-white color, which re- 



