STATE GEOLOGIST. 125 



Alluvial and drift materials, 



Bow no, ( Woodville,) 7'.) ft. 



low, 40 it. 



Bituminous coal, 



Highly an oaccoua fire clay and sandstones, 20 ft 



Shales, below, dark, bituminous I 



. with thin seams of coal, 1 



Bhalc , 38 ft 



ma,) 105 it 



The whole thickness of the coal measures here, between the 

 overlying and undei lying sandstones, is thus shown to be 123 



feet, which is the greatest Ibiokness yet measured, 

 however, the thi< so. 



Patting all the observations together, (of which it is in 

 essarv to m.ikc any further details,) it appears that the rocks 

 of the coal measures occupy a shallow basin, the Longest 

 of which is nearly coincident with the axis of Saginaw bay. 

 This bay breaks over the northeastern rim of the basin, and 

 near its head the rocks will probably be found to exhibit their 

 greatest depression. It is not likely, however, that this depres- 

 sion varies greatly between Saginaw and Ionia county In 

 other words, the lowest depression of the carboniferous trough 

 lies beneath a line extending from Ionia county into Saginaw 

 bay. Along this line the coal measures will be found to have 

 eatest thickness, and the coal seams will oc developed in 

 gieatcst number and force. 



\V1k n we speak of the carboniferous basin or trough, it must 

 nevertheless be remembered that all these rocks repose very 

 nearly in horizontal planes, so that the slight undulations into 

 which they have been thrown by gentle distal 

 solid.; Lave presented em 



Subsequent! 7 been more or I : i down. It follows, there- 



fore, that the Woodville sandstone is not eve:; found 



ares, even within the area that has been 

 ■ 

 landstone, or into the sbale i 

 as to ; 'iie coatoeams. 'I lie t rcr, within 



thecarbonifen coal, 



