Hollow Earth: The Long and Curious History of Imagining Strange Lands, Fantastical Creatures, Advanced Civilizatio Read Free Page A

southwestern coast. Arriving in 1677, there he spent a year mapping the night sky, returning in 1678 to produce a catalog of the celestial longitudes and latitudes of 341 stars—the first of its kind for that hemisphere and a considerable aid to navigation. As we’ll see, navigational concerns led Halley to his theory of the hollow earth, as he attempted to explain variations in the earth’s magnetic poles.
    The magnetic compass had come into use during the twelfth century; and while valuable in a general way, sailors soon found that compasses had the annoying habit of significantly deviating from true north. Worse, there was no evident pattern or consistency to the magnetic variation. The lines of the earth’s magnetism bend away from true north, and at any given place these variances themselves vary over time. Understanding the causes might lead to the ability to predict variation and thus compensate for readings that had been misleading sailors for centuries. (Another difficulty lay in New World real estate; territorial boundaries established with simple compasses caused constant legal wrangling as magnetic variation shifted.)
    Here was a problem as significant as that of establishing accurate longitude.
    Halley had more than a passing interest in magnetic variation. He had investigated the puzzle for years before presenting his 1691 papers and spent several years afterward at sea, primarily mapping magnetic variation in the South Atlantic. Understanding its causes promised potential long-term rewards, but detailed chapter-and-verse charts of current observed deviation were of immediate pragmatic value. His 1701 magnetic charts of the Atlantic and the Pacific were the first such published, as well as the first to connect points on the oceans with the same variance, using lines now called isogonic lines—also the first published.
    He had made his first observations on magnetism as a sixteen-year-old schoolboy and continued them four years later during his long excursion to St. Helena. Magnetism was one of the great unknowns. It had been recognized as a force since ancient times, but nobody had a clue what it was. Sailors, for example, believed the powerful fumes given off by garlic somehow interfered with the proper working of the compass, and they wouldn’t allow the stuff onboard.
    The earliest scientific ideas about magnetism came from William Gilbert, eventual physician to Queen Elizabeth, who in 1600 published De Magnete after eighteen years of study and experimentation. In it he suggested that the earth is a vast magnet, explaining for the first time why compasses point north. Descartes had a go at a theory of magnetism in his 1644 Principia philosophiae, involving his famous fluids and vortices, but it was as wrong as it was ingenious.
    The major work on the subject was Athanasius Kircher’s 1641 Magnes, both exhaustive and a little cuckoo, a perfect emblem of the man himself. Kircher, a German Jesuit born in 1601, combined polymath erudition and intellectual eccentricity in ways far beyond those of mortal men. He is often mentioned as a candidate for “the last man to know everything,” from obscure archaic languages and literatures to the latest in science to the most fantastical absurdities then in currency, all in heaps in the measureless attic of his remarkable mind. He was, as we used to say in the 1960s, a trip. He wrote forty-four books on subjects ranging from Egyptian hieroglyphics to possible causes of the bubonic plague, constructed strange objects (including an automatic organ), and assembled in Rome what was arguably the first natural history museum.
    Kircher’s Magnes, as one account describes it, “contains all that was known in his day on the subject of electricity and magnetism … filled with curiosities, both profound and frivolous. The work does not deal solely with what modern physicists call magnetism. Kircher discusses, for example, the magnetism of the earth and heavenly bodies; the