STATE GEOLOGIST. 201 



circulation of the water, in these strata, prevent it from sinking, 

 in these elevated sections, to the level of the lowest portions of 

 the basin in remote parts of the State. As a consequence, arte- 

 sian borings might prove successful throughout the southern 

 half of Jackson county, and the eastern portion of Calhoun, if 

 continued down to the bottom of either of these groups. 



It must not be supposed, however, that the artesian wells of 

 Jackson are supplied from this source. If I have succeeded in 

 the identification of the rocks in that vicinity, these wells are 

 • supplied from the Parma Sandstone Albion is outside of the 

 rim of this formation, and the wells there have to be continued 

 down to the bottom of the Napoleon Sandstone. Marshall is 

 outside of the rim of this, and rests just upon the rim of the 

 outcropping Marshall Group; and hence I should not expect 

 that the contained waters would rise to the surface. The arte- 

 sian (salt) wells of Grand Rapids are supplied from the Napo- 

 leon Group, the water being salted from the group immediately 

 above. The wells at Saginaw issue from the same sandstones, 

 and are salted in the same way. In the southern part of Jack- 

 aon and northern part of Hillsdale counties, where the streams 

 have cut through these rocks, the contained waters rush out in 

 extended chains of most beautiful and copious springs of 'pure 

 water. Adrian is located upon the argillaceous strata of the 

 Huron Group, and the first water-bearing stratum which would 

 be reached is included in the Monroe limestones, perhaps 250 

 feet below. But the surface slopes gradually toward Lake 

 Erie, so that the hydrostatic pressure would not be adequate to 

 an artesian overflow. Ann Arbor is supposed to lie within the 

 rim of the Marshall and Napoleon sandstones, but the consider- 

 able elevation of this place precludes all expectation of an 

 overflow. The artesian wells at Toledo do not reach the selid 

 rock at all, though this has been unsuccessfully explored to a 

 considerable depth. The alluvial deposites, which are here of 

 great depth, are made up of alternating sandy and argillaceous 

 beds, which slope gradually toward the bed of the lake, and of 



26 



