The evening Argus., 1867-01-15

original form in which the meta kas deposited and
that the carbonate was formed by its oxydation.
3
"Again, it may be observed that the filing of the
crevices with the metaferous matter is shown, by
many circumstances connected with the mode of oc-
eurrenee of ores in this region, to have taken place
from above downwards, general thing, while ev-
idence of the introduction of metalliferous solution
from below, by thermal springs otherwise, seems
to be wholly wanting. The termination Of the crew.
before reaching the upper sandstone, the entire
absence of ores in this rock and the mpossibihty OF
procuring evidence of the existence of
disturbances of the rocks faults, are among the
most convincing proofs of the mode of deposition
having been made from above, while several 'ns'''h
ces have been observed in which the position Oh the
mass ore was such to show, beyond tine Possiohty
of doubt, that the metaliferous solution eouid NOT
have been introduced into the hssure iroh peio"'
"Tn the first place. it seems evident that the metals
in ouestion must have been held in solution in the
oceanic waters from when the ROCKS oil the north
west have been thrown up
As corroborative of this theory, the writer
of this may mention that In several instances,
IN ad-bsaring caves, he has seen what may
be termed galena stalagmises and stalaotities.
That 49, from the roof of the cave would de-
pend a regular stalactite composed OF lesd
ore, with q small percentage OF spar.
Immediately beneath this would bs staiag-
mite of exactly the same material as the 9th
or, and evidently formed by 'droppings"
from above. The theory of Prof. Whitney is
the one which receives the largest measure
of assent, although there are not wanting
great many mining experts who hold snd
will battle for theories which are entirely
different.
f9- FORMATION OF PRAIRIEs.
One of the most interesting papers in this
volume is one by Prot. Lesquereux, on the
origin and formation of prairies. Apart
from the purely scientific interest of such
an inquiry, there is much value attached to
ii from the light which such an Investigation
throws upon the composition of prairie soils,
and their proper management.
The theories of Professor Lssquereux, with
reference to the formation of prsiries, are not
new nor given to,the public for the first time
in the present volume of the geological sur
vsy, While to Professor Lesouereux belongs
tho credit Of their original discovery, their
appearance in the Illinois survey is simply
transfer from other sources. For the ben
eft of those who do not have access to soien-
tihc publiosslens, the main points of Profess
or Lesquereux's theory are appended.
Prairies are formed by the over flow and
their recession of the waters OF lakes and
rivers. When the lake waves or currents
strike the shores or low grounds, and there
hesp materials, sand, pebbles, mud, etc.,
they Suild up more or lees elevated dams or
islands, which soon become covered with
trees.
These dams frequently inclose wide, shall
low basins, whose waters are thus prevented
from moving. These sheltered places become
filled with aquatic plants, and, after e time,
the waters become dried up by evaporation
and infltrstion. .....
This is, In the briefest possible language,
the theory in regard to the formation of prai-
riss. Why trees do not grow upon prairies
is thus explained:
s'The termination of seeds of arbbrescent plants
needs the free of oxygen for its development
and trees especially in their youth, absorb by the
roots great amount of air and demand solid point
of attachment to which to fix themselves. Moreover
the acid of this kind Of soil, by its particularly
tseptc property, promotes the vegetation of pecu-
liar growth of plants, mostly herbaceous. 0fall
trees, the tamarac is the only species which, in
northern, climate, can grow peaty ground; and
this, eyen happens only under and favorable
circumstances; that is, when stagnant water, re-
manning ut constant level has been invaded by a
kind of MOSES, the sphngnuzn. By their powers OF
absorption, their continuous growth and the rapid
accumulation of their remains, these slowly
raise the surface of bogs above water and it there
in this loose ground constantly humid but accessible
to the atmosphere that the tamarac appears.
CONCLUSION.
The conciuding portion of volume | is de-
voted to the geology of the counties Of the
state. Some finely tinted maps accompany
this portion of the report; aud generally il
may be said that Messrs. Worthsrn and En-
geimsnn have succeeded in aking this per