'/ 



129 



formations above the disturbed strata just referred to, in conformity to 

 each other. The distance between these two points is three hundred 

 and fifty or four hundred miles. The thickness of the formations here 

 is very small when compared with those of the Alleghany region. 

 Hence the basin-like curve between these points is not great, giving the 

 appearance of almost horizontally within moderate limits. 



The lower portion of this basin consists of an immense deposite of 

 magnesian limestone ; the upper, of the limestones, sandstones, shales, 

 and coal of the great western coal basin. The magnesian limestone 

 deposite is subdivided by a well marked deposite of siliceous «andstone, 

 generally light-colored, often perfectly white and friable. The lower 

 'vision of the magnesian limestone is light brown, or ashy in color, 

 very compact or hard, but decomposing with considerable rapidity when 

 exposed to atmospheric or aqueous influences. In Missouri it presents 

 many interesting views of precipices, caves, natural bridges, &c. At 

 rame du Chien it rises about one hundred feet above the level of the 

 "ver, but in Missouri, in the vicinity of Eangua River, it rises much 



higher. 



on very much in litho- 



°gical character, it differs entirely, so far as it has yet been explored, 



« being totally deficient of fossils and nearly or quite so of valuable 



nerals. Its entire thickness has never been determined. As there 



treasons to believe that it belongs to a distinct geological epoch, and 



an lr nportant economical purpose will be served in discriminating 



w een it and the upper division, Dr. King proposed to call this the 



bUa llm estone ; this name being of course only provisional, and 



18 a «d the Appalachian region it shall be found to be only a continu- 



one of the latter series, or when a satisfactory systematic no- 



aure shall have been adopted by American geologists generally. 



°ve this dirision of the magnesian limestone deposite, lies the sand- 



ia ^. alread y referred to, and which appears rarely to exceed fifty feet 



^ ickncss. It i s remarkably uniform, being almost identically the 



is ■ e ^ n t,H ckness and lithological character at Prairie du Chien that it 



% pos> S ° Ulhern P art of Missouri. Above this, in Wisconsin, is a de- 

 tw l e ° ,lme stone, in strata of various thickness, making in all about 



co ^ ° r tlMrty feet > remar kable for thc abundance of the fossils, for its 

 diff lnm ^^ e se ams of a brown coal-like matter,- and for its marked 

 or b ^ nCe *** ^ho'ogical character from the magnesian deposits above 

 tho ii i/ " ^ n S did not find this fossiliferous limestone in Missouri, 

 the WQS not P re P ared to deny its existence there. Judging from 



j a S^nious tracings of the New York formations westward by Mr. 

 ®* Hall, Dr. K. was willing to admit the high degree of probability 



* LV '», No. l.-April-June, 1844. 17 







