136 Notice of Geological Surveys. 



ascent, they would lie at an elevation above low water mark of 

 the Ohio, of nearly three thousand four hundred feet. 4. Grant- 

 ing these particulars, or that only a portion of the rocks were con- 

 tinuous, the only authorized explanation of their absence, is a 

 grand denudation by diluvial causes, which have operated in the 

 general direction of this anticlinal axis of the blue limestone, and 

 reduced this extensive area to one of a nearly uniform elevation. 

 The immense diluvium on the Ohio, and in all the northern part 

 of Indiana and Illinois ; the bowlders of primitive rocks ; the 

 masses of native copper in Indiana ; the buried trees of Ohio, all 

 indicate a mighty current from the northward, that has modified 

 most remarkably the contour of the whole country. 



The history of the agencies that have operated on this conti- 

 nent to give it its present face, can never be completely written 

 from a comparison of the various elevations of the different parts, 

 but the evidence presented by stratification, diluvium, and other 

 geological resemblances, will, on the contrary, do far more to elu- 

 cidate this subject, if it do not clear it up entirely. 



in. Second Annual Report of the State Geologist of the State of 

 Michigan ; made to the Legislature, Feb. 4, 1839. 



The deficiency of maps of this state is so great that it is im- 

 possible to appreciate or understand much of the topography of 

 its northern and unsettled portion, and much of the minute evi- 

 dence on which the geological conclusions are based, is with- 

 held for the final report. In general, the rocks of the northern 

 part of the state belong to the carboniferous group, and "in this 

 respect coincide with those heretofore described as occupying the 

 southern counties, though their position in the series is very dif- 

 ferent." 



" They consist of a succession of limestones, with intervening 

 shales, sandstones, and clays, and at the northern extremity of 

 the peninsula, the limestone is shattered in a manner similar to 

 that seen in the sandstone in the southern counties." 



The direction of all the rocks is northeast and southwest. Sa- 

 ginaw Bay, on Lake Huron, lies in the line of bearing, its south- 

 ern shore being sandstone, and its northern limestone, both of 

 which may be traced across southwesterly to lake Michigan. The 

 limestone is observed at numerous points going north, at times so 



