Two portraits of Edmond HalleyPatricia Fara

Clare College, Cambridge, UK CB2 1TL

Edmond Halley is most famous for vindicating Isaac

Newton’s theories by predicting the return of the comet

that now bears his name. As well as being an accom-

plished and ambitious astronomer, Halley also initiated

important theories about the earth’s magnetic patterns

and suggested many navigational reforms. Halley’s por-

traits reveal that he was proud not only of his innova-

tive map showing how an eclipse would be observed

over England, but also – more surprisingly – of his

theory that intelligent life exists inside subterranean

magnetic cavities.

Modern science owes much to Edmond Halley (1656–1742). Isaac Newton may have been England’s greatestgenius, but it was Halley who pushed him into writing thePrincipia, even shouldering the publishing costs himself.A brilliant mathematician, Halley revised Newton’sobservations and carried out the complex calculationsneeded to predict the return of the comet now named afterhim. When it appeared on cue some 20 years after hisdeath, Halley’s comet convinced even sceptical Frenchastronomers that Newton’s theories were right.

Unlike many of his sedentary colleagues, Halley was anadventurous researcher whose exploits included captain-ing an Admiralty ship to South America, testing his owndeep-sea diving-bells, and spying out foreign coasts forQueen Anne. Because international travel was so importantfor Britain’s economy, Halley strove to reform navigationscientifically. His theories about the earth’s magnetism –vital for correcting ships’ compasses – were essentiallyunchallenged well into the 19th century, and he inventedrevolutionary systems of map-making still in use today [1].Halley not only became Britain’s leading astronomer, butwas also active in economics, introducing statistics into theshady world of life insurance and running the Mint atChester. Little wonder that Peter the Great invited him todinner for free advice about improving the Russian Navy!

But by bringing Newton into the limelight, Halley casthis own accomplishments into shadow. He did, however,advertise his own activities in his portraits. In Figure 1,although his left elbow is resting on a larger-than-lifevolume by Newton, his right hand – the one traditionallyused by gentlemen for important oratorical gestures – ispointing to his eclipse map of England, which shows ablack ellipsoidal shape lying centrally within a diagonaldark band. Painted about five years later, this picturecelebrates Halley’s success in predicting the passage of thesolar eclipse that had darkened southern England in 1715,the first in London since 1104.

Halley published this map to demonstrate how power-fully mathematical astronomers could control apparentlyrandom natural phenomena. He had calculated the area oftotal eclipse and devised this new visual technique to showat a glance how it would sweep across the country. On22 April, excited visitors from Paris joined Halley andother Fellows of the Royal Society as they observed theeclipse. By carefully organizing a network of correspon-dents throughout the country, Halley set up a nationalexperiment, which recorded the eclipse so accurately thatmodern scientists can use his data to estimate changes inthe sun’s diameter [2].

When he posed for his last portrait (Fig. 2), Halley was afrail 80-year old. That significant right hand is holding adiagram he had produced over 40 years earlier to depictthe earth’s internal magnetic structure. PresumablyHalley felt that this magnetic model was important, yethe and his colleagues had scarcely referred to it in theintervening decades. Halley was world-famous for hissimpler version, in which a fluid buffer separates an innermagnetic globe from an outer magnetic crust, so that theearth has two pairs of magnetic poles rotating gradually

Figure 1. Oil painting of Edmond Halley, attributed to Isaac Whood, c. 1720. Repro-

duced, with permission, from the National Portrait Gallery, London.Corresponding author: Patricia Fara (pf10006@cam.ac.uk).

Review Endeavour Vol.28 No.2 June 2004

www.sciencedirect.com 0160-9327/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.endeavour.2004.02.002

with respect to one another. For the more complicatedmodel he chose to illustrate in his last portrait, Halleydescribed an outer crust of ‘Magnetical Matter’ 500 milesthick, which surrounds three inner globes whose diam-eters are proportional to those of Venus, Mars and finallyMercury, a solid ball 2000 miles in diameter.

Still more unusually, Halley maintained that theintervening spaces are inhabited. Although he neverspecified the details of this intelligent life form, he didlater suggest that it was maintained by special subter-ranean light, which escaped and became visible during anaurora borealis. Why should a young astronomer who wasstruggling to establish his reputation make such anapparently bizarre proposal? One answer is that Halleywas trying to rebut allegations of atheism. When hepresented his paper to the Royal Society, he was applyingfor the Savilian chair of astronomy at Oxford, and rumourscirculated about his orthodoxy: Halley was, alleged one ofthe electors, ‘a skeptick and a banterer of religion.’ Halleyused his semi-hollow earth to support the Christian beliefthat the universe is not eternal. He postulated an etherthat was gradually slowing down all the heavenly bodies.Making the earth less dense would, he argued, explain

why this aether had not swept the moon away to become anindependent planet [3].

Halley established his religious credentials still furtherby bringing God directly into his argument. By maximiz-ing the interior surfaces of the earth, Halley claimed, Godhad provided extra living space for further inhabitants,just as multi-storey buildings enable more people to besqueezed into cities. He spelled out his motives: ‘I haveadventured to make these Subterraneous Orbs capable ofbeing inhabited,’ he explained, ‘designedly for the sake ofthose who will be apt to ask cui bono, and with whomArguments drawn from Final Causes prevail much.’ [4].Nevertheless, Halley’s rhetorical tactics make it unclearhow firmly he believed in his own multi-shell model.Anticipating objections, he argued tentatively, promising amore polished account if this preliminary attempt shouldbe well-received – although a revised article never didappear.

The Oxford chair went to another candidate. Butalthough Halley had failed to demonstrate his religiousorthodoxy, extraterrestrial life did become part ofNewtonian orthodoxy. By the time this diagram resurfacedin his portrait, many people believed that intelligentbeings existed on other planets in our own solar system aswell as on planets surrounding stars throughout the entireuniverse. Halley was probably the first astronomer to useNewtonian arguments for this plurality of worlds, whichremained important in debates about science and religion[5]. Cotton Mather, an American preacher at the RoyalSociety, informed his readers that ‘Mr Halley allows theremay be Inhabitants of the lower Story, and many ways ofproducing Light for them.’ Many natural theologiansagreed with Mather’s exuberant advocacy of life else-where in the universe: ‘Great GOD, what a Variety ofWorlds hast thou created!’ he exclaimed; ‘Who can tellwhat Angelical Inhabitants may there see and sing thePraises of the Lord!’ [6].

References

1 Fara, P. (1996) Sympathetic Attractions: Magnetic Practices, Beliefs,and Symbolism in Eighteenth-Century England, Princeton UniversityPress

2 Cook, A. (1998) Edmond Halley: Charting the Heavens and the Seas,Clarendon Press, pp. 351–353

3 Schaffer, S. (1977) Halley’s atheism and the end of the world. Notes andRecords of the Royal Society 32, 17–40.especially pp. 17–18

4 Halley, E. (1692) An account of the cause of the change of the variation ofthe magnetical needle; with an hypothesis of the structure of theinternal parts of the earth. Philosophical Transactions 16, 563–578.p. 577

5 Fara, P. (2004) Heavenly Bodies: Newtonianism, natural theology andthe plurality of worlds debate in the eighteenth century. Journal for theHistory of Astronomy, forthcoming

6 Mather, C. (1721) The Christian Philosopher: A Collection of the BestDiscoveries in Nature, with Religious Improvements, pp. 109–110, p. 19

Figure 2. Oil painting of Edmond Halley by Michael Dahl, 1736. Reproduced, with

permission, from the Royal Society of London.

Review Endeavour Vol.28 No.2 June 200458

www.sciencedirect.com