CHAPTER X. 



COAL MEASURES. 



In regular order of succession, the carboniferous limestone for- 

 mation is followed by a complex of sandstone and shale deposits 

 with intermediate seams of coal, termed coal measures. 



This series occupies the central portion of the Lower Peninsula, 

 and is supposed to cover about one fifth part of its entire surface ; 

 but over its greater extent the formation is hidden by drift de- 

 posits, and its limits on the north and west sides of the basin are 

 rather taken for granted than known. The thickness of the formation 

 could be ascertained in a few localities only ; it seems in Michigan not 

 to exceed 300 feet, and is often less — a thickness which, compared 

 with the development of the coal measures in our neighboring 

 States, Ohio and Illinois, is very insignificant. In proportion 

 to the thickness of the formation is also that of the inclosed 

 seams of coal, of which we generally find only one of sufficient 

 thickness for mining enterprises, while our neighbors can boast of 

 six or seven productive beds, besides a number of smaller interme- 

 diate seams not taken into account. 



The approximate limits of the coal measures on the peninsula 

 are within a line drawn from Sebawing, on Saginaw Bay, toward 

 Holly, in the south part of Genesee County, and from there pro- 

 longated in a southwesterly curve to Jackson. From Jackson the 

 line goes west, passing a few miles north of Albion ; it then strikes 

 northwest, passing some distance east of Bellevue, to Hastings, 

 whence, northward, the extent of the formation is only guessed at. 

 The western edge of the coal measures is supposed to intersect the 

 Detroit and Milwaukee Railroad line near Lowell, thence to go 

 north, touching Big Rapids, and from there to run in a north- 

 eastern curve, diagonally through Osceola County and the north- 

 west corner of St. Clair County. The line does not seem to trans- 

 gress the second correction line ; it goes parallel with it along 



