472 WISCONSIN STATE AGRICULTURAL SOCIETY . 
a range of hills over 400 feet high. To the east of Barahoo, where this range 
of hills is brought to a point by the passage of the Wisconsin river around 
it; the center of this belt is exposed. An intensely hard quartzite, with a 
softer silicious rock with a slaty structure, sometimes passing into a talcose 
slate or what resembles it very much, forms here the center or backbone of 
this belt, which is covered mostly with the Potsdam sandstone. At Devil’s 
lake, and at the narrows where the Barahoo river passes through the gap, 
there are beautiful exposures of this quartzite. Also on the south side of 
the hills a little to the west of the Sauk road, and seven or eight miles still 
farther to the west on the north side, are fine exposures of the same rock. 
But where this belt intersects this north and south anticlinal, there is, I be¬ 
lieve, no more quartzite; at least, I have not seen any. 
Whether this quartzite, forming in places, if not continuously, the center of 
this range of hills, is a metamorpliic sandstone of the Potsdam age, or of 
some older formation, our geologists are not all agreed. But upon this point, 
I think there can be no difference of opinion. To change sandstone of any age 
into a quartzite like this, there must have been intense metamorphic action 
along this line at some period in the past. It is, however, from this point of 
intersection west, that this belt becomes of great interest in a practical point 
of view, and I propose to notice it carefully. 
Along this range of hills in the region of Baraboo, the lower bed of sand¬ 
stone (Potsdam) is the surface rock. But extending west from this, the lower 
magnesian limestone forms a considerable portion of the higher land, the 
sandstone always exposed along the valleys, giving us often good exposures 
of the junction of those formations. Where they are found in their normal 
or unaltered condition, they gradually pass into each other by alternate 
layers of sandstone and limestone, each layer becoming thinner as it passes 
away from the bed to which it belongs. But from this general rule there is 
a marked departure along this belt. The silica, which in these alternate 
layers is usually found in the form of sand, is here found in the form of flint, 
hornstone and chert, and these in some places passing into a hard, whitish, 
clayed rock, all no doubt different forms of the same material. This clayed 
form has been taken by some for gypsum, and although it resembles it in 
some of its earthy forms, it is, I think, destitute of the elements of that com¬ 
posite. It may nevertheless be of economic value, and I may refer to it 
again in another place. 
These forms of silica, such as flint and hornstone, are not always found, 
like the sandstone, in layers or beds between the layers of limestone, but very 
often mixed up with it. Nor is this peculiar feature of the strata uniform 
throughout the region; in some places we find the sandstone and limestone 
in their normal state. Nor does it extend up very far into the thick beds of 
limestone, nor down very far into the sandstone, but is confined to the sub¬ 
ordinate layers of the two formations. It extends, nevertheless, over a large 
portion of this belt, and where it has been exposed as the surface rock to 
denudation, large pieces of flint and hornstone lie scattered over the sur¬ 
face. 
