426 WISCONSIN STATE AGRICULTURAL SOCIETY. 
ditions, such as would seem to be produced in harmony with 
the above facts and considerations would not fail to produce 
the forces I have referred to; that such forces both chem¬ 
ical and mechanical, would not fail to produce physical dis¬ 
turbance along the line of strata in which and along which 
they act; that such disturbances would not fail to produce 
phenomena that would correspond to their action, and that 
would possess features by which we might possibly recognize 
their cause. It is now a well established fact that all natural 
phenomena possess and present more, or less distinctly, the 
evidences and material for their own explanation. If then, in 
the light furnished by the above facts and considerations, the 
phenomena of the lead district begin to assume forms and 
features by which we can recognize them as the result of 
physical conditions such as are described above, in the absence 
of other facts to explain them, it is perfectly legitimate and 
safe to follow this light as far as it will lead us. 
After this momentary digression, I will return to pursue 
again our investigations along the north side of the mining 
region. On the north side of the elevation along which the 
sink holes are found, the surface is very much broken, and 
declines rapidly toward the valley of the Wisconsin Eiver. 
The streams also flowing into this valley cut back into this 
elevation, in places almost to its centre. 
This rapid declivity to the north, and the gradual dip of the 
strata to the south bring to the surface on the north side of 
this elevation the strata of the lead district, that is, the rocks 
in which the mines have been worked, and let us down on the 
lower rock, namely, that which underlies the mines of the 
lead district. Here we find ourselves on a platform at least 
400 feet below the surface of the lead district, and on rocks 
that were formed long before the rocks of the lead district had 
any existence. This, too, places us back in the history of the 
past to a period when the temperature of the cooling crust of 
the earth, and other physical conditions were very different 
from what they were during the formation of the rocks of the 
lead district. 
