Appendix—Geological survey . 
481 
Those beds of kaolin that we find resting on the surface of the rock, along 
the line of this granite belt, although beneath the soil, are no doubt formed 
from the decomposition of the feldspar of the granite by the action of the 
water. The water may be in its ordinary condition, but held in depressions 
on the surface; or it may contain some peculiar solvents obtained from the 
decomposition of some other portion of the rock; or it may be water with 
more than ordinary dissolving powers reaching the rock through springs. 
But this change takes place no doubt always in the presence of water, and 
through its agency. This belt of rocks, extending for fifty miles east and 
west, peculiarly feldspathic, and covered in many places with extensive 
marshes, that are fed with living springs, affords the condition for the for¬ 
mation of kaolin that is but very seldom found in this or any other country. 
The properties of kaolin, especially its refractory properties, have been 
known from a very early age. The Orientals, away back in the dim past, 
recognized these properties, and used this material in the manufacture of 
their best porcelain, or as it is generally called, “ china ware.” Nor has the 
increasing light of science and art, from that period, down to the present, 
discovered or prepared material superior to kaolin for this purpose. It is 
peculiarly adapted for pottery, and can be manufactured into such articles 
with every degree of skill. Wherever extensive deposits of kaolin are 
found, with the usual facilities for manufacturing and transportation, pot¬ 
teries will sooner or later be established. These refractory properties render 
it very valuable also for various other purposes, such as fire bricks, fire clay, 
retorts , and other vessels used for metallurgical purposes. In this connection 
I may refer to it again in another part of this report. 
On the sides of this granitic belt, and especially on the south side, so far 
as there is a chance to examine them, these rocks appear to be changing into 
a slaty character, although no doubt they are related rocks, for I notice in 
places that the granite passed gradually into gneiss, and the gneiss into rocks 
of a slaty structure. From this they pass into the well known slate rocks that 
form a considerable portion of azoic strata, such as mica, talcose, and chlo¬ 
rite slates. These strata are traversed with veins of quartz from one to twenty- 
five feet wide. In some places, the quartz is very hard and vitreous, in others 
of a softer kind, more porous, and mixed with an irony clay. This class of 
rocks is well exposed on the Wisconsin river, and also on the Black river, 
but away from the streams on this east and west line, they are mostly covered 
with sand and sandstone, beneath wdiich the azoic formations are well covered 
to the south. 
The metalliferous character of this belt is well exposed along the Black 
river, near the Falls. The prevailing ore, so far as we can judge from surface 
exposures, is iron. Of this ore, two varieties are prominent, namely, a dark, 
fine-grained magnetite, and the red hematite. They differ from each other, it 
is true, in their physical characters, but resemble each other very much in 
that they are mixed considerably with silica in the form of quartz, so as to 
make the ore, as a general thing, rather lean. 
The mode of occurrence here, conforms strongly to the prevailing type of 
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