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Episodes 2009; 32(2): 114-124

Published online June 1, 2009

https://doi.org/10.18814/epiiugs/2009/v32i2/004

Copyright © International Union of Geological Sciences.

Desmarest’s “Determination of some epochs of nature through volcanic products” (1775/1779)

Kenneth L. Taylor

Department of the History of Science, University of Oklahoma, Norman, OK 73019, USA. E-mail: ktaylor@ou.edu

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In 1775, Nicolas Desmarest (1725–1815) presented an interpretation of geological evidence he had been examining for over a decade, among the extinct volcanoes of Auvergne in south–central France. He interpreted the volcanic remnants in that region in terms of three successive epochs, distinguished from one another by their degree of erosive alteration and the different topographic positions they held following extensive denudation. He insisted on the utility, for the establishment of sequential stages in the region’s history, of what he called his ‘analytical method’ of working backward in time, from recognition of the most recent and therefore least altered products, to reconstruct in the imagination those more thoroughly disturbed and confusing remnants of earlier periods. In addition to being a landmark effort in historical geology based on local observation, Desmarest’s paper was also notable as an expression of what would come later to be called uniformitarian thinking: he argued that the erosive processes responsible for wearing down the lavas must have operated gradually and constantly. While Desmarest seems never to have wavered in his view of volcanic action as a subordinate agent in the overall dynamics and history of the globe, he showed awareness that his analysis of the Auvergne lavas pointed toward a considerable role for volcanism during long portions of the province’s geological history.
The nearest thing to a contemporary publication of Desmarest’s 1775 presentation came more than three years later, in the form of an ‘excerpt’ in the February 1779 issue of the journal Observations sur la physique. An English translation of that excerpt is presented in the present paper for the first time.