464 
WISCONSIN STATE AGRICULTURAL SOCIETY. 
taken place along the line of the fissures. As as an evidence 
of this, we always find beneath this cap-rock (as it is called) a 
seam extending from the sides of the opening horizontally, di¬ 
rectly beneath the cap-rock; and it is where this horizontal 
seam intersects the vertical fissures, that the decomposition takes 
place, and the ore is deposited. As a consequence of this, we 
find these openings, not only along the same range of fissures, 
but along the same horizontal plane. This is a fact worthy of 
a moment’s reflection, and its teachings should be heeded. 
These deposits of ore are always found beneath this cap-rock, 
and never above it. Query : Was it introduced from above or be¬ 
low ? In openings like this, where the rock has been decom¬ 
posed between two or more fissures running parallel to each 
other, we find not only clay and sandy material, the results of 
decomposition, but often large pieces of partially decomposed 
rock, which bear the appearance of having been acted upon by 
strong solvents. These openings vary in size, and are found 
from five to forty feet wide, and from ten to fifty deep, contin¬ 
uing from one hundred to several hundred feet in length, and 
they often yield from one to five million pounds of ore. 
The material in these openings is not a disorderly, incohe¬ 
rent mass, but is arranged mechanically and chemically under 
some general law peculiar to this form of deposit. The finer, 
softer material, such as clay and ochre, is arranged along cer¬ 
tain lines, while the carbonate of lime dissolved out ot the 
decomposed rocks is re-deposited in the form of calcareous 
spar, to form with the finer part of this clay and ochre, a matrix 
in which these ores are deposited. In such openings, it looks 
as though the medium in which and through which, these sol¬ 
vents or dissolving agencies acted, furnished also the solutions 
from which these ores were formed; as though nature first 
prepared the place, and then deposited her treasure. 
In the early history of our mines it was thought that where 
these openings closed in depth was the limit in vertical range 
of our ore deposits; but subsequent mining has shown that 
they succeed each other in the downward course of the fissures, 
and now not only the second but the third, and in some places 
