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tion, botli of a practical and purely scientific character, and wliicli could 

 not be transferred to the maps, nor be suitably embodied in the annual 

 reports, has been compiled from my field notes, arranged for future re- 

 ference, and for such use as may be found advisable in the final report 

 on the survey. Particular attention has been devoted towards the full 

 collection of all such datails as would give a completeness to the several 

 objects aimed at, in this department of the survey, and I may be per- 

 mitted to say that no source of information known to me, has been neg- 

 lected, which could subserve interests of so important and comprehen- 

 sive a character. 



PURPOSE OF PRESENT REPORT. 



The Report of Mr. Douglass, of last year, embraced a general view of 

 the extent of the coal bearing rocks, so far as then ascertained, and their 

 details in the counties of Jackson, Ingham, and Eaton; my own having 

 been confined to the rocks below the lowest of the coal bearinir series. 

 Without further recapitulation of the facts heretofore submitted, than 

 may be unavoidable, I propose, in the present report, to exhibit a com- 

 prehensive view of all the rock formations, throughout the oiganized 

 counties of the State. 



The " Geological Section," hereto prefixed, will serve to exhibit at a 

 glance, the succession of the rock formations, from the universally su- 

 perimposed sands and gravels, down to the great limerock formation of 

 the southern portion of the State, bordering on Lake Erie. It is in- 

 tended to show the rocky basis which would be exhibited to view, if the 

 country could be cleft through, in a line from Lake Erie to Maple river, 

 . in Clinton county. The rocks in this Section, are grouped according to 

 their distinguishing characters and relative position, and each group is 

 distinguished by an alphabetical letter. The sub-divisions of some of the 

 groups, are given in the body of the report. 



GENERAL GEOLOGY OF THE ORGANIZED COUNTIES OF MICHIGAN. 



In the "Section" alluded to, the rocks embraced within the district 

 under consideration, are divided into groups, as follows : 



A. Erratic Block Group, or Diluviums. — a. Alluvions, ancient, 

 recent. 



B. Tertiary clays. 



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