The British Library
The Shadow Of The Moon

An Exhibition Of British Solar Eclipse
Mapping In The Eighteenth Century.
 
The exhibition is curated by Geoff Armitage, author of the recent book of the same title, copies of which are available for purchase in the Library's Bookshop. The exhibition is located in the lobby at the entrance to the Maps Reading Room onthe 3rd floor of the British Library at St Pancras, 96 Euston Road, London NW1 2DB (nearest tubes: Kings Cross/St Pancras or Euston). Additional examples of eclipse mapping will also be on display in the "Treasures of the BritishLibrary" in the Ritblat Gallery on the upper ground floor for the next few weeks, where there are other maps on permanentexhibition. Map Library is open Monday 10-5, Tuesday to Saturday 9.30-5; the Library building is open seven days. 
 
INTRODUCTION

Although nowadays we regard eclipses of the sun as natural albeit spectacular astronomical events, even as late as the eighteenth century they were thought to be the work of the devil.  Eclipses have been predicted and diagrams drawn of them from at least the time of Aristotle and Claudius Ptolemy, but true eclipse maps, in the sense of geographical maps showing the paths of eclipses are a phenomenon of the eighteenth century onwards.  Diagrams of solar eclipses occur in the Renaissance versions of Ptolemy's astronomical work the Almagest and, for example, Peter Apian's Cosmographicus first published in 1524.  Accurate predictions, however, did not emerge until Edmond Halley (1656-1742) revolutionised astronomy and introduced the eclipse map and many other scientific thematic maps which influenced map-makers for the rest of the century and beyond.

 
Letterpress broadside map predicting the annular eclipse of 18 February 1737 by John Haynes.  Although this is rather crudely engraved it is an unusual example of a very decorative eclipse map in colour.
Maps CC.5.a.59.
2 This complicated-looking geometrical diagram by Joseph Crosthwait shows how the 1715 eclipse would appear in the London area.  The geographical type of eclipse map was much easier to understand and therefore more successful.
Maps *23.(1.).
 
3 A broadside by Thomas Taylor for the 1724 eclipse reflecting the fairly sophisticated nature of these separately sold sheets. 1t contains detailed information, written and visual, about how and why an eclipse occurs.  The attractive view at top right shows people observing a total solar eclipse.  Maps (unallocated).  
4 The first ever eclipse map, by Edmond Halley, predicting the eclipse of 1715.  Halley also made history by predicting the timing to within four minutes.  The heavily shaded oval disc represents the umbra or moon's shadow.
Maps *23.(2.).
5 Detail of a solar eclipse on John Speed's world map from A prospect of the most famous parts of the world (1627).  Although this is decorative and illustrates the cause of solar eclipses, it is not particularly informative.
Maps *920. (48.). (Photocopy).
6 Diagram of a solar eclipse from the Almagest by Claudius Ptolemy.  This was published in 15 3 7 but the information dates back to Ancient Greece.  Eclipses have been scientifically observed from Antiquity particularly for their use in determining longitude.
Maps C.c.2.(3.). (Photocopy).
 
7 Chart by William Rogers (1738) showing the appearances and times of eclipses in London until 1760.  Although no total solar eclipse is shown, the 1748 eclipse was total over Scotland and there were annular eclipses in 1737 and 1764 over Ireland and Scotland and south-cast England respectively.
Maps *23.(7.).
 
8 York mathematician George Smith invented this skewed projection to depict the path round the globe of the 1737 eclipse.  The map also includes digit lines and double circles to indicate the appearance of the sun at various locations.
Maps *23.(10.).
9 Laurie and Whittle.  'Multi-track' retrospective eclipse map showing the tracks of the 1715, 1724, 1737, 1748 and 1764 eclipses, published in 1794.  The 'Century of eclipses' was rounded o]T with maps such as these., but the eclipse paths are very approximate.
Maps 177.e.2.(10).
10 Map by Charles Desnos predicting the annular eclipse of 1764 over Europe.  This is a rare example of black and sepia colour printing in the 18th century, achieved by using two separate copper plates.  The map also features digit lines and a decorative cartouche.
Maps 185.m.2.(3.).
11 Map predicting the 1737 annular eclipse by self-taught Durham astronomer Thomas Wright.  This map is very accurate and in the classic Halley tradition, but with the addition of 52 double circles to indicate the amount of obscuration of the sun in different locations.
Maps 177.d.l.(19.).

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