APPENDIX—GEOLOGICAL SURVEY. 
4.G9 
principal fissures); in these places the fissures close up to a 
seam, but the seam continues as far as explored. Along the 
streams in the lead district, where this rock is exposed, no 
well defined fissures are noticed. Poorly defined, irregular 
fissures, however, traverse the rock in all directions, and in 
connection with them we sometimes find evidences of chim¬ 
ney-like perforations, such as those referred to before. In the 
belt of iron ore to the north of tbe lead district, we find 
fissures and ranges of fissures in this rock, with openings 
similar to what we find in the limestone. And from the fact 
that deposits of ochre and oxide of iron are found along this 
belt in connection with fissures, it is possible that deposits of 
ore of some kind may be found in the rocks below the mines 
in the lead district; but of this we have no evidence. The ' 
fact, however, that we cannot prove that these fissures will be 
productive in or below this rock, does not prove that they may 
not be. At this point let us examine the evidences furnished 
in similar ore districts where this has been tested. 
“ In Cumberland, 1 lodes of lead ore occur in carboniferous limestone^ 
which alternates with sandstone and argillaceous shales. The lodes are 
only broad and productive when enclosed in the limestone, split up into 
branches and non-productive in the sandstone and shales.” 
“ In Derbyshire, 2 the beds of the metalliferous limestones are separated by 
beds of Basaltic rock, called toadstone. When a vein of lead is worked through 
the first limestone down to the toadstone, it ceases to contain any ore, and 
often entirely disappears; on sinking through the toadstone to the second 
limestone, the ore is found again, but is cut off by a lower bed of toadstone^ 
under which it appears again in the third limestone. In strong veins par¬ 
ticles of lead occur in the toadstone, but in very small quantities.” 
I might multiply quotations here to show that ore districts si¬ 
milar to this of Wisconsin, and found in different parts of the 
world have had to contend with difficulties arising from the ir. 
regularity of their ore deposits, produced by beds of barren rock 
intervening, as great, and in many instances greater than those 
presented by the few feet of sandstone that divides the lime¬ 
stone beds of the lead district; difficulties which enterprise 
has overcome or accident has removed. How insignifi- 
1 Ore Deposits. Page 47. 
2 Bakewell’s Introduction to Geology. Page 304. 
