84 GEOLOGICAL RECONNOISSANCE 
The chert slope at 340 feet in this section is nearly on a level with the 
chert slope of the previous section. This formation seems to cap gene- 
rally the subordinate ridges from 500 to 550 feet above Buffalo, but there 
are other ridges, off to the south, which must be nearly double this height. 
The rocks which constitute the preceding sections, have the lithological 
aspect and chemical composition of the rocks which form the hills on both 
sides of the Upper Mississippi, between the mouth of the Chippewa and 
Black river, and around Lake Pepin, referrible to the age of the Potsdam, 
sandstone and calciferous sand-rock of the New York system. 
Geology being decidedly a science of comparison and analogy, I may 
venture to predict, in the absence of all systematic mining operations, 
from my former experience in other similarly constructed countries of the 
north-west, as well as from what has already been observed in Marion and 
Carroll counties, in Arkansas, that lead ore will be found, to some extent, 
in the rocks of Newton county ; but, in all probability, somewhat irr egularly 
disseminated in “ pockets,” “ crevices,” “ strings,” and horizontal openings 
through the rocks, rather than in regular bodies; hence, mining operations 
will be attended with some uncertainty, and considerable labor and 
expense; still, where the surface indications are encouraging, and the 
calcareous rocks predominate over the sandstones, they may be undertaken 
by those having the necessary experience in rocks of this description, with 
considerable prospect of success, so soon as the district is supplied with 
furnaces for smelting the ore ; but not with as much profit to the miner as 
in a cherty limestone, a member of the subcarboniferous formation, which 
we shall have occasion to mention hereafter. 
In consequence of the southerly dip of the rocks, most of the strata of 
the preceding sections disappear in succession beneath the waters of Cave 
creek, as we ascend that stream. 
On the waters of Cave creek, about six miles above its mouth, a liver- 
colored marble-limestone forms the base of a cliff, at an elevation of 10 to 
20 feet above the bed of Cave creek, overlaid by cherty limestone. Several 
nitre-caves have been formed by the disintegration of the liver-colored 
marble limestone under the cherty limestone. The principal nitre-cave is 
on the property of J. 8. Thompson, on section 27, township 15 north, 
range 19 west. 
The dark brown nitre-earth, which forms the floor of this cave, is rich 
in salts of nitric acid, owing, no doubt, to the large quantity of organic 
matter incorporated with the earth. The nitre-earth has been traced for 
50 to 60 yards back into the cave, and for 7 to 8 feet in depth, mixed with 
tumbled rock. 
Time has permitted, as yet, only a partial qualitative examination of 
