90 REPORT OF THE 



answer the requisites of a coarse grindstone, and some years 

 ago this manufacture had attained here a considerable degree 

 of importance. 



The Napoleon sandstone outcrops at numerous other locali- 

 ties in the south part of Jackson county, and further northwest. 

 Being entirely destitute of fossils, it is not easy to distinguish 

 it from the sandstones above, and the unfossiliferous portions 

 of the sandstones below. The most northern exposure yet ex- 

 amined on the southern slope of the State, is in the right bank 

 of the Grand River about a mile above Grandville, in Kent 

 county. 



In all the borings for salt which have passed through the 

 Napoleon sandstone it has been found separated from the Mar- 

 shall Group by a bed of clay. This, at the State salt well, was 

 14 feet thick; at Lyon's well, 9; at Butterworth's, 10; at Scrib- 

 ner's, 10; at the Indian Creek well, 15; at Windsor's, 10; at 

 East Saginaw, 64 feet. The thickness of the overlying sand- 

 stones is pretty uniformly about one hundred feet. 



The Napoleon sandstone bears considerable resemblance to 

 the conglomerate of Ohio, as seen in the gorge of the Cuyahoga, 

 at the falls; but it contains no pebbles, and occupies a position, 

 moreover, below the carboniferous limestone. As a distinct 

 formation, therefore, it has no satisfactory equivalent in sur-' 

 rounding States; and there is no reason, except its negative 

 palaeontological characters, for separating it from the Marshall 

 Group. The uniformity in the petrographic character of the 

 sandstones of Huron county, has already been alluded to. 

 Should it hereafter appear that the separating shale which lies 

 between the Marshall and Napoleon Groups of the southern 

 part of the State is wanting in the north, we shall be obliged 

 to regard the one hundred and nine feet of sandstone passed 

 in the deep well at East Saginaw as representing both these 

 groups, diminished to the thickness of one of them; while the 

 shale beneath, penetrated to the depth of 64 feet, must be re- 

 garded as the commencement of the argillaceous portion of the 

 Huron Group. Such a thinning of strata toward the north 



