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THE GEOLOGICAL TIME-SCALE.
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Professor Le Conte has proposed Psychozoic, on the same principle for the latest geological period, in which man has appeared. (See Le Conte, Elements of Geology, New York). Lyell proposed to make, on this basis, a geological time-scale and applied the term Period to each of the several divisions of the scale. Thus we find in his Geology, second edition, published in 1841, a recognition of the time element in classification, without as yet the adoption of the biological nomenclature. He gives a table "Showing the order of superposition, or chronological succession, of the principal European groups of fossiliferous rocks. Under the heading "Periods and Groups" we find the following:

I. Post-Pliocene Period A. Recent.
B. Post Pliocene.
II. Tertiary Period C. Newer Pliocene.
D. Older Pliocene.
E. Miocene.
F. Eocene.
III. Secondary Period G. Cretaceous group.
H. Wealden group.
I. Oölite, or Jura limestone group.
K. Lias group.
L. Trias, or New Red sandstone group.
M. Magnesian limestone group.
N. Carboniferous group.
O. Old Red Sandstone, or Devonian group.
IV. Primary fossiliferous Period—P. Silurian group.
? Q. Cambrian group.

(Lyell, Elements of Geology, second edition, London, 1841. Vol. ii, p. 178).

Later Lyell adopted the biological nomenclature, and was prominent among geologists in developing and elaborating the idea of the successive appearance of new types of organisms coördinate with the progress of geological time.

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