Historical Geographies of the Prime Meridian: the Case of France and Britain in the Eighteenth Century

Institute of Historical Research
Paris-Sorbonne University

Historical Geographies of the Prime Meridian: the Case of France and Britain in the Eighteenth Century
Charles WJ Withers
(Edinburgh)

Repondent : Daniel Foliard (Paris Ouest-Nanterre – La Défense)
Abstract: The Prime Meridian is the line at which the world’s longitude is set at 0˚. Both longitude on the
one hand, and time’s measurement on the other, are based on the Prime Meridian. Since 1884, the
Prime Meridian has been fixed at the Royal Observatory, at Greenwich, in the United Kingdom. The
fact that Greenwich is the ground zero of planetary measurement is the result of recommendations
made at the 1884 International Prime Meridian Conference, held in Washington DC, in 1884. Before
1884, however, there were many different prime meridians at work in the world. This was a source
of considerable geographical and astronomical confusion.

In this paper, I examine the relationship between two different prime meridians, those of Paris
and of Greenwich in the ‘long’ eighteenth century and do so through the lens of the historical
geographies of science. The paper will explore, firstly, the debates between international politics,
national mapping, and the local siting of the Paris prime meridian in the period c.1634 to c.1787,
and, secondly, the workings of joint Franco-British attempts to ‘fix’ the prime meridians of Paris
and of Greenwich by triangulation in the period c.1787 to c.1830. The paper is about rockets, maps,
metrology, and trust in instruments, about the politics and authority of science and about the
reliance placed upon questions of accuracy and precision and the tolerance of error as nations
delimit themselves.

Franco-British History seminar series

Author: 
School of Advanced Study, University of London
Speaker(s): 
Charles WJ Withers (Edinburgh)
Event date: 
Thursday, 20 November 2014 - 12:00am
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