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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume IV (1876-1877)

Day, F. H.
On the fauna of the Niagara and Upper Silurian rocks, as exhibited in Milwaukee county, Wisconsin, and in counties contiguous thereto,   pp. 113-125 PDF (4.1 MB)


Page 113


Fauna of the Niagara and Upper Silurian Rocks.  113
ON THE FAUNA OF THE NIAGARA AND UPPER
    SILURIAN     ROCKS AS EXHIBITED           IN MILWAU-
    KEE COUNTY, WISCONSIN, AND IN COUNTIES
    CONTIGUOUS THERETO.
                        BY F. H. DAY, MI. D.
                     Wauwatosa, Wis., Dec. 27, 1877.
  It is stated as an axiom by high paleontological authority,-
that "Since rocks are identified more by theirfossil contents, than
bv their lithological character, a name descriptive of the latter
is of less importance than formerly, when fossils were the sub-
ordinate characters of a mass;" and although paleozoic char-
acters have assumed the supremacy over all others in distinguish-
ing sedimentary strata, " still the lithological terms must not
be
overlooked; for if properly understood, they will be unerring
guides in tracing the condition of the surface, for more than hun-
dreds of miles in extent."
  Changes in the lithological features of a rock which may render
observations unsatisfactory, are accompanied by greater or less
variation in the nature of the fossils. It is therefore of the high-
est importance in the examination of sedimentary rocks to be gov-
erned by three essential facts, which are:
  1st. The lithological character.
  2d. The order of the superposition.
  3d. The contained characteristic fossils.
  By an observance of such precepts geologists have been enabled
to form a reliable and a systematic geological history, which is ar-
ranged into natural distinctions of ages, periods, epochs, and eras,
with the capability to trace from one portion of country to another,
through all intricate phases, types and characters, the rocks con-
taining remains, images or casts of paleozoic life.
  It is thus we determine the first appearance in the world's his-
tory of organized beings, as exemplified in thecommencement of
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