Yorkshire Type Ammonites, Vol. 2

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Excerpt from Yorkshire Type Ammonites, Vol. 2: The Original Descriptions Reprinted, and Illustrated by Figures of the Types, Reproduced From Photographs Mainly by J. W. TutcherIn 1903 (quart. Journ. Geol. Soc. LIX, 461) some of these terms were expanded by the use of 1967 and 3726 into six series of percentages of a base-line, the radius 100 (see also Mon. I. O. Amm., 1905, p. Cxcvii).It is obvious that a base-line founded on the radius was correct for the breadth of the whorl, and, in fact, is the only one possible, because the breadth of the whorl must vary within that limit, reaching possibly to 100 per cent. Of such base-line. But a base-line founded on the diameter would give incorrect values for the breadth of whorl, which in an extreme case might reach to no more than some 55 per cent. Of such base-line. Then a base-line founded on the radius gave quite satisfactory results for the thickness of the whorl, though, in abnormal cases, the thickness exceeds 100 per cent. Of such base-line. But a base-line founded on the diameter, though not giving results so unsatis factory as in the case of the breadth, would afford less discrimination among 'the numerous thin-whorled forms, for the longer the base-line the larger the number of whorls which would be called thin. And there is the same objection to a long base-line in regard to the nomenclature of umbilication. All these considerations in¿uenced the choosing of a short base-line such as the radius.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.