468 
WISCONSIN STATE AGRICULTURAL SOCIETY. 
also in the vertical range of the same fissures. One other fea¬ 
ture of this class of fissures here, and everywhere else, is, the 
ore-deposits conform to the stratification, and instead of 
making a continuous vein along the wall of the fissures, they 
form a series of deposits along their vertical range. Hence we 
have in the galena limestone, the first, second and third open¬ 
ings, and sometimes the fourth. In the blue limestone beneath, 
we have the brown rock opening, the upper pipe-clay opening, 
the glass rock, or dry-bone opening, the lower pipe-clay open¬ 
ing, all following each other in succession along the vertical 
range of the fissures. 
As each of these successive openings has been reached, and 
the fissures below them have again contracted and become 
poor, there has been reason to doubt the probability of ore 
being found below. For many years after the mines in the 
galena limestone were opened, not a man could be induced to 
spend a day in prospecting in the blue limestone ; it was 
looked upon by both practical and scientific men as a barren 
rock. But now, and for many years past, our best mines have 
been found in this formation. It has been by a series of acci¬ 
dents, almost, that we have stumbled upon these lower depos¬ 
its, believing only when we saw them. 
But now we are down upon a bed of sandstone about 80 or 
100 feet thick, from beneath which there dawns no light. Sci¬ 
entific men are divided in their opinions in reference to it; 
some contend that it is only a temporary barrier, others that it 
is the bottom of our mineral formation. This certainly is one 
of the most important questions connected with our mining 
interests in the lead district; one upon which the future of 
these interests must depend. And while it is important 
that we approach this question with care, and avoid theories 
formed on imperfect data, it is likewise important to collect 
all the information we have, or can obtain on this point, to 
direct us in future operations. 
We know but very little about the character of the fissures 
beneath our productive mines when they enter this sandstone ; 
it has been reached in but two or three places, (and not near the 
