STRATIGRAPHICAL GEOLOGY 
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Yorkic Period of Stratigraphy. In a recent recalculation, ad¬ 
justment, and evaluation de novo of the periodic time-units so 
that the span of all subdivisions of geologic chronology of this 
rank may be subequal, the Devonic and Siluric (Upper) divisions, 
as commonly recognized, proved altogether too short. The first 
of these was only about two-fifths, and the second only about 
three-fifths, of a normal unit. Together their time-span equaled 
that of other periodic divisions. 
Use of the title Yorkic in this connection is a recognition of 
the circumstance that in New York state is displayed the most 
complete development of the (Upper) Siluric and Devonic sections 
in the world. It is not in any sense an adaptation of the early 
New York System of Emmons, Mather, Vanuxem and Hall, in 
1842 and 1843, because the limits of their section were coterminous 
with that vast rock-pile now recognized as spanning the Paleozoic 
era. Delimitation lines of the major subdivisions of the New 
York System are approximately those of the European classifi¬ 
cation which was already properly defined when the New York 
proposal first appeared in print. 
In view of the fact that the Murchison Siluria embraced vir¬ 
tually the entire Paleozoic section, that he, himself helped to de¬ 
tach a considerable upper portion under the title of Devonian 
System, that Sedgwick removed a lower part under the term of 
Cambrian System, and that Lapworth closed the bitter Murchison- 
Sedgwick controversy by suggesting the name Ordovician System 
for the disputed middle section — the Lower Silurian of the one 
and the Upper Cambrian of the other — there is only-left of the 
original Murchisonian succession the Upper Silurian rocks which 
constitute a quite subordinate portion of the whole. 
And now when the time values of sedimentation are alone to be 
considered, or measured, the last remnant of Siluria merges into 
a later adjudication. Rather than attempt to extend Murchison’s 
title so as to include the Devonic section where the latter original¬ 
ly reposed, or to restrict the original definition, it appears to serve 
better the canons of modern geologic nomenclature to drop the 
old names and adopt an altogether new title, remove the typical 
section to the locality where involved rocks find best development. 
