“We have Adventured to Make the Earth Hollow”: Edmond Halley’s Extravagant Hypothesis Peter W. Sinnema University of Alberta This essay revisits Edmond Halley’s schema of a multi-sphered, hollow earth, presented to the Royal Society in 1691 as a hypothetical resolution to the problem of magnetic variation. I open my investigation with a reading of Michael Dahl’s ªnal portrait of the great astronomer (1736), which enig- matically reproduced a diagram of the hollow earth that Halley had ap- pended to his original “Account [. .] of the Internal Parts of the Earth” in the Philosophical Transactions. My essay has the goal of enhancing our ap- preciation not only of Halley’s aptitudes as a theorist of the earth sciences, but as the dexterous practitioner of a language felicitously attuned to the early development of that ªeld. I provide a comprehensive exposition of Halley’s self-styled “Extravagant” hypothesis and argue that his attachment to it was sustained by his adherence to the tenet of a divinely ordained, natural economy. I also position Halley’s “Account” as the originary moment of a lit- erary sub-genre—the hollow earth fantasy or romance—that ºourished in England and America in his wake. Today, Dahl’s painting gestures simul- taneously to Halley’s conception of a habitable inner earth and to a literary tradition that embraced that idea as its central imaginary novelty. 1. Halley’s Enigmatic Legacy Portrait In 1736, an 80-year-old Edmond Halley, digniªed by the academic robes of his alma mater, Queens College Oxford, sat down at the brush of trans- planted Swedish artist Michael Dahl for his ªnal ofªcial portrait.1 (Fig. 1) By the time he posed for Dahl, Halley occupied a rank of distinction among practical philosophers of the early Enlightenment. His manifold achievements included authorship of the ªrst catalogue of stars in the 1. Halley left Oxford in 1676 without completing a degree, but was created M.A. per literas regias in December 1678. Perspectives on Science 2014, vol. 22, no. 4 ©2014 by The Massachusetts Institute of Technology doi:10.1162/POSC_a_00144 423 Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/POSC_a_00144 by guest on 02 October 2021 424 Halley’s Extravagant Hypothesis Figure 1. Michael Dahl, “Dr E Halley, Aged 80.” (1736) © The Royal Society. Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/POSC_a_00144 by guest on 02 October 2021 Perspectives on Science 425 southern hemisphere, the laying of actuarial foundations for life insurance and annuities, his correct prediction of the return in 1758, 1835, and 1910 of a bright periodic comet that today bears his name, his steady en- couragement (and personal ªnancing) of Isaac Newton in the writing and publication of his world-changing Principia Mathematica,2 his 1703 inves- titure into the Savilian professorship of geometry, and some sixteen years’ service as Astronomer Royal. Halley’s intellectual fertility, like his reputa- tion in senectitude, was prodigious. Viewers may reasonably look to the aged astronomer’s legacy portrait for a visual commemoration of his dis- tinctive charisma. Herein I investigate Dahl’s painting as a most peculiar memorial, one of two Halley portraits in the Royal Society’s picture collection3 that serve as reminders of his many contributions to that institution in its pursuit of “Natural Knowledge”: as an elected Fellow from 1678 (re-elected 1700) until his appointment as Clerk in 1686, in which ofªce he also edited the Philosophical Transactions for six years—contributing more than eighty pa- pers of his own over the course of nearly six decades—and as the Society’s secretary from 1713–21. My discussion of the portrait’s formal properties, however, moves quickly into a more protracted consideration of the eso- teric geophysical theory to which it pays homage, a hypothesis about mag- netic variation (or declination) and the earth’s shell-like structure that Halley presented to the Society in 1691 and published in the Philosophical Transactions the following year. Although the connection between portrait and scientiªc proposition has been commented upon before—most nota- bly by Patricia Fara in the second chapter of Fatal Attraction (2005) and again in the pages of the Notes and Records of the Royal Society (2006), but also cursorily in other Halley biographies and histories of hollow earth theory4—this particular instance of ideological provenance awaits a com- prehensive exposition that attends sympathetically to the language and imagery of its original articulation. My account of the story behind Dahl’s portrait has the goal of further enhancing our appreciation not only of Halley’s aptitudes as a theorist of the earth sciences, but as the dexterous practitioner of a language felici- tously attuned to the early development of that ªeld—that is, as a gifted and persuasive rhetorician on matters geological and cosmological. I also 2. “Stimulus, critic, sustainer, editor, publisher: bringing forth the Principia was [Halley’s] greatest contribution to natural knowledge” (Cook 1998, p. 178). 3. The second, by Thomas Murray, is discussed brieºy below. 4. See respectively Fara 2005, pp. 41–50 and 2006, pp. 199–201; Armitage 1966, pp. 70–75; Cohen 1972, pp. 62–66; Kollerstrom 1992, pp. 185–192; and Standish 2006, pp. 15–36. Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/POSC_a_00144 by guest on 02 October 2021 426 Halley’s Extravagant Hypothesis want to argue, with necessary brevity, for Halley’s self-styled “Extrava- gant” hypothesis as the originary moment of a literary sub-genre—the hollow earth fantasy or romance—that ºourished in England and America in his wake. Today, Dahl’s painting gestures simultaneously to Halley’s conception of a habitable inner earth and to a literary tradition that em- braced that scheme as its novum or “central imaginary novelty” (Csicsery- Ronay 2008, p. 47). In both cases, I draw attention to a shared assumption about cosmic structure, the belief that nature persistently displays frugal- ity of composition. Halley’s stubborn attachment to the hollow earth model cannot be explained biographically. Rather, his adherence, however guarded, to a theological doctrine commonly held in the seventeenth century—that creation is “as copious as possible” because “that would log- ically be part of the Creator’s plan” (Standish 2006, p. 32)—also sustained his allegiance to the radical globe-within-a-globe hypothesis. In Halley’s dotage, as Duane Griffen puts it, this idiosyncratic theory remained “a perfectly plausible proposition” (Griffen 2012, p. 3), not only because it responded cogently to breaches in empirical knowledge but be- cause it transitioned smoothly from geophysics to the related domain of theology—to the idea that a muniªcent Providence would prescribe the habitability of a cavernous underworld. Dahl’s portrait attests to the hol- low earth idea’s perseverance into the 1730s, less as the quirky persuasion of its inventor than as a scientiªcally viable response to the question of magnetic variation that also harmonized with the law of utility. Divine economy in turn came to function as the base logic in various works of prose ªction, revealing ideological linkages between the scientiªc theory and its subsequent, imaginative representations. One of the earliest hollow earth novels, the anonymously authored Voyage to the World in the Centre of the Earth (1755), demonstrates my point with exemplary gusto. This “history” embedded its rudimentary chthonic setting within the grander mise-en-scène of a providentially—and efªciently—organized uni- verse. The result is an analogically complex fantasy, which opens with the unnamed narrator tumbling into a crevice at the top of Mount Vesuvius, falling through “a little more than a hundred Miles” of outer crust, and landing in a “World . plac’d directly in the Centre of our Earth” (Voyage 1755, p. 22). In this pleasant subterranean kingdom, where “everything grows spontaneous” thanks to a constant and agreeable temperature, the narrator encounters an abstemious civilization whose moral perfection is akin to “the Christian Religion in its Purity, and without Adultera- tion” (Voyage 1755, p. 87). The Voyage is a prolonged exploration of an idealized political and social state that contrasts violently with the real- ity of superterranean existence: whereas “Plainness and Sincerity is the Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/POSC_a_00144 by guest on 02 October 2021 Perspectives on Science 427 Characteristic” of life underground, with the Europeans all is “Shew and Ostentation” (Voyage 1755, p. 250). The novel ultimately suggests that a hollow earth is typologically in- dicative of a sublime providential plan—a point of contact between Hal- ley’s hypothesis and the hollow earth tradition that was to take root in early nineteenth century America, as I discuss in my concluding remarks on that tradition’s seminal work, Symzonia. At one point the Voyage’s narra- tor is introduced to Mr. Thompson, another earthling who has lived hap- pily underground for one hundred years as a sort of benign natural philos- opher. Thompson’s experiences as a submerged surface dweller lead to his ªrm conviction that every planet in the universe must be either inhabited or suitable for habitation. “For my own Part,” Thompson tells his rapt listener, till by mere Accident I was thrown upon this Central World, I had no Idea of there being one, and inhabited, in the Bowels of the Earth. In short, these Things are Wonderful to us; yet tho’ we can- not comprehend, our Wonder ceases, when we consider that all this is the Work of an omnipotent Being. How vain are we then to at- tempt to search into his Ways, and to pronounce those Things im- possible, that we cannot comprehend? [.