56 Wisconsin and Missouri Lead Region. 
iron, being found at the point of contact, I am led to the opinion © 
- that the granite is the more recent rock, and that more veins may 
with confidence be looked for along and near its line of junction 
with the limestone. 
. Not only do sandstone beds alternate with the limestone, but 
in the vicinity of known lead mines, particularly, the limestone 
comprises heavy beds of a cavernous, siliceous rock, exceedingly 
hard, like the French burrstone, and like it:sometimes suitable for 
millstones. There.too abound in it mammillary and botryoidal 
masses of quartz rock coated with erystals, veins of calcareous 
spar, known by the name of “iif,” and lumps and beds of he- 
matite iron ore, all which are now considered in Missouri indica* 
tive of the proximity of lead ore veins. These, unlike the copper 
ore veins noticed, occur at a distance from the granite, which 
agrees well with the position of lead and copper mines in Corn- 
wall ; tin and.copper being there: found near granite, and lead, 
antimony, manganese, iron, &c. at a distance from it. 
. The sandstone does not to my knowledge contain veins of 
ores ; these are every where in the limestone; and in those places 
where the sandstone is the prevailing rock no mines are wrought. 
.This rock is occasionally useful as a building «stone, for furnaces 
particularly; and it sometimes occurs of a suitable quality for the 
manufacture of glass, as at a: me four miles east of misesgeT: 
on the Farmington road. 
-. The lead ore occurs in various ways, frequently: in eamiand 
strata in the red elay overlying the rock; in true rock veins; 
which are subject to all the variations in thickness, in richness 
and to all the changes that the better known veins in the primary 
rocks are; and also in vertical fissures in the limestone, either in 
loose “chunks” in the clay which fills these fissures, or in regular 
horizontal layers at intervals across them, or incrusting the walls 
of the fissures, accompanying then» as far as they are followed: 
When the fissures open out.into what appears to have been a large 
cave, now filled with clay and mineral, the ore incrusts each side 
of the roof and floor, while: within is the clay and. sometimes an 
Kd : cay ae — et 298 2g. ete 
MS Baas to keiatt ae bee teased oma. 3 
