Dodgeville chronicle. [volume] (Dodgeville, Wis.) 1862-current, 1871-12-22
MINING DEPARTMENT.

Ir the history Of our planet no line,
perhaps, is more distinctly drawn than the
one that divi les the azoic system from the
palaezoic system. Nature almost made a
pause here, and when we can sit down
for moment and study on, the one hand
Rhs physical conditions that prevailed prev
ious TO the introduction OF vegetable and
animal life, and ON the other hand. the
physical conditions that prevailed at the
a;ne when they were introduced, and that
prevailed through the subsequent cycles
of time that has been bringing these forms
of life to their present state OF perfection:
The azoic system, as its name implies,
81 characterized by the entire absence Of
organic life I; and the presumption is that
she temperature Of the cooling crust Of the
=, earth was such at that, period as to pre-
clude the possibility Of the existence of
such organisms. The palsezoic system,
If which the petsdam sandstone is. the
0rst member in this State, is characterized
by the dawn Of vegetable and animal life
: and the physical conditions under which
shss. forms Of Ifs subsequently, crowded;
both land and water. Between the physi
y. cal conditions Of those two systems there
Z. marked difference that we do well to-
: remember when we examine the relation
tAev bear to each other, especially when
they meet, as they do in the strata under
consideration. ,
irhe prevailing rocks Of tho azoic system
are she' well known states; such as ehiorite
,alcos and the argillaccous states, inter
.,ra,itisd with beds Of hornblendc, gneisss
and other rocks of apparent sedirnentory
origin. that have been changed, in their
/ character by exposure to intense and long
continued heat. 1t is true that the beds
.>.ofyrss,ite, trap, and o;herarocks OF igneous
1FiSin: that we occasionally End protruding
these strata, may have contributed some.
8 what 10 the metamorphic action of the age.
but the great TRANSFORMING power OF that
neriod was the gaseous subllmations,,
: ,stesfn. and vapor that must have been
continually rising fIo,n the intcror, Hence,
abe lines Of fracture, and disturbances that
evsrywsere marked the surface ct the ACC
rocks. u.
Regular and well defined systems of
svkes A., also peculiar TO the axoic for.
nation, and at their point OF contact the
evidences of mctamorphic action and mec-
hanical disturbance are very distinct
These poinss Of contact seem also to be
!, centers of force, marked by alternate
!, aeriod of activity and repose, and we have,
in various places in the world, abundant
evidence to prove that lug after the phys
teal conditions we've such as to admit Of
aqueous formations and, animal life above
shem, that periods of activity have return
ed and stamped the very impress OF those
dykes and cerS.ers Of force on this newly
formed strata. al HOB
Now, while the formed rocks OF the pal.
aeozoic system, with their fossie remains
o. of vegetable and animal organisms, may
rspose undisturbed on the azoic rocks a.
q. way Fl ON those iises Of fracture and sys
TENS of dykes yet over them changes and
transformations in these newly formed
rocks. are known to have taken place for
hundreds, in some instances for thousands.
Of feet.
Axes of elevation, lines of physical dis
surbances, impregnations of matter, and
sucb like phenomena as characterized the
lead district, and the region to the north OF
II, are in many places the known results OF
such causes. On the south shore OF Lake
Superior we find the line where these two
syste,ns meet, and where both can %
i II ssssssEa fton TIE same standpoint, where