COAL MEASURES. 1 45 



a coal seam has been ascertained. Last fall they commenced to 

 sink a shaft to the coal bed, but since then I have not heard how 

 far the work has advanced. 



The coal fields of Michigan, supposed to cover a space of 8000 

 square miles, are up to the present day of very inferior importance 

 in the economy of the State. Only four mines are in actual opera- 

 tion, and these are worked with but a small force of men. 



Searching for the causes of this neglect of apparently so great 

 stores of wealth buried beneath our feet, we find one of them in the 

 imperfect exposure of the rock beds, which, with the exception of 

 those in a few limited districts, are all deeply covered by drift de- 

 posits. This would be no serious impediment, if the coal seams 

 were spread in a continuous sheet over the surface of a certain 

 horizon ; we could then without much risk go down and uncover 

 them ; but all coal deposits are confined originally to certain limit- 

 ed basins, and if we consider that the coal ^series, as the youngest 

 of the stratified rock beds found on the peninsula, has been with- 

 out protection by later deposits, exposed to the vicissitudes of 

 untold ages, we must expect to find a large proportion of the 

 deposits destroyed and swept off ; in particular, during the drift 

 epoch, the coal formation mult have suffered immense destruc- 

 tion from the moving glacier masses. The direct proof of this is 

 furnished by the large quantity of debris of the coal measures 

 mixed with the drift material ; but the drift action has not only de- 

 stroyed a large proportion of the coal formation, but has at the 

 same time filled up the eroded gaps with loose drift material, hid- 

 ing the extent of destruction from observation, and thus rendering 

 our mining operations always hazardous in a deeply drift-covered 

 region, because we have no means whereby to know how much of 

 the supposed underlying rock strata has escaped destruction. 



The same erosive forces have acted on the coal formation of Ohio, 

 but there the valleys of erosion intersecting it have not been filled 

 again with drift masses. The erosion has rather facilitated access to 

 the coal beds, and laid the strata open for observation in natural 

 sections miles in length. There success to miners' enterprises is 

 assured by the same revolutionary forces which have proved so det- 

 rimental in the case of ours. Another reason for the small de- 

 velopment of the coal-mining industry in Michigan is undeniably 

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