
The geography of the great solar eclipse of July 14 MDCCXLVIII 1748. Allen LRO 91
On July the 14th 1748 George Smith, an astronomer, surveyor and mathematician from York, mapped out the path of a solar eclipse. A narrow band on ‘The geography of the Great Solar Eclipse of July 14th MDCCXLVIII...’ marks the extent of the total eclipse while around the outside of the map numerous Suns show the amount of shadow from various locations. What bad luck to be just outside the range of total cover!

We know that Smith’s map was made before the eclipse, as it was published by Edward Cave, ‘according to act of Parliament’, in January of that year. Both the Chinese Empire and the empires of the Golden Crescent kept records of eclipses dating back thousands of years and these records have been used to record the changes in the Earth’s movement and for accurately dating historical events. But it wasn’t until the eighteenth century and the works by astronomers such as Edmund Halley* in improving tables recording the journey of the Sun and Moon through the sky that enabled maps such as Smith’s to be able to show the predicted course of the eclipse as opposed to recording this after the event.

An earlier 1724 eclipse map has an interesting story attached to it, highlighting that most common cause of compliant, plagiarism. John Pryer’s map ‘A Pocket Companion of ye Roads of the South Part of Great Britain, called England and Wales…’ is not what it first appears. Originally printed in 1724 the map shows the road system of England and Wales giving distances between major towns and cities and is similar to a host of road and travelling maps published around the same time.

Overprinted onto the original map is additional information tracking the path across the Southern parts of Ireland and England of a solar eclipse on the 11th of May, 1724. The map’s title makes no mention of the eclipse, the only reference to the eclipse on the map states ‘the faint parallel lines drawn cross this map show the passage of the shade of the Moon over England in the total eclipse of the Sun on the 11th day of May 1724 in the afternoon‘ suggests a map showing where the total eclipse will fall.
Pryer’s map is a copy of an earlier map with the same title by Herman Moll, from 1708. This map went through several editions and was copied, both legitimately and not, a number of times. It’s presumably Moll who has included a complaint against copyists in a piece of text on the map as another version of the map held at the Bodleian includes the note ‘This map has ben copied four times very confused and scandalousy’
‘Since ye beginning of this new sett of maps now completely finish’d, several ignorant pretenders have started up & with great shew & noise frequently advertised their trifling performances: calling them cheap, curious, useful & correct: as to the first epithet, they are really dear at any price; in ye 2d. place , everybody may see they are wild, confused and poorly engraven; as for their usefulness, they tend only to lead people into errors; and so far from being correct, that the projection of their principal maps is notoriously false’.
It is not recorded whether Pryer is one of Moll’s ‘Ignorant pretenders’, though the lack of any mention of Moll and his map makes it likely that Pryer used Moll without authority, though if so you do have to wonder why he would include the diatribe against unscrupulous publishers and cartographers if he was one himself.
The 1724 eclipse was well mapped. Another version by Edmund Halley also includes the path of a 1715 eclipse as well.

A description of the passage of the shadow of the Moon over England in the total eclipse of the Sun on the 11th day of May 1724 in the evening... Vet A4 a.13 (6) 1724
We know this map was published after the eclipse as text, presumably by Halley, alludes to earlier predictions on the path of the eclipse and how this map showed ‘the passage of the shade as it really happened; whereby it will appear that tho our numbers pretend not to be altogether perfect, yet the correction they need is very small’.

The doctrine of eclipses, with particular account of the great eclipse of the Sun & Earth which will happen the 11th of May 1724. Vet A4 a.13 (14) [1724]
The ‘earlier predictions’ can be found in a doctrine of eclipses printed, presumably, a few months before the map. As well as complex set of instructions and diagrams the doctrine also includes a perfect description of what an eclipse is, ‘An eclipse is the loss of light really, or in appearance, in any of the heavenly bodies, caused by interposition of one of the planets, and is either Solar, Stellar of Planetary’. The doctrine, which seems to have been published as a pamphlet, also includes a World map showing the path of the total eclipse.

Finally, the cover of an Ordnance Survey map showing where the path of the eclipse can be seen in England on the 29th June, 1927. The map shows levels of totality and times (an early start, as the eclipse started at 5 a.m.). Typical of Ordnance Survey maps of the time the cover is a delight.

Eclipse maps are amongst the most fascinating of the type, showing a celestial event where objects millions of miles away fall into line creating a magical event on Earth, an event made more interesting by the fact that through careful calculations, tables and records kept we can now accurately predict when and where these events will happen. Even though science has taken the mystery away to be in the path of a total eclipse is still a magical event.
*Halley was a man of many talents. As well as improving the records for the motions of the Sun and Moon crucial to predicting eclipses he also made accurate measurements of magnetic variations throughout the World, tried to establish the date of Stonehenge and, most famously, predicted the course of a comet that would come to bear his name. For a while Halley lived in a house close to the library where this blog was written, underneath Oxford’s version of the Bridge of Sighs.





















































