The Age of Louis XIV

by Will Durant

  The ingenious and inconclusive Hooke opened a hundred promising avenues of investigation, but was too poor in funds or patience to follow them to famous ends. We find him everywhere in the history of British science in the second half of the seventeenth century. Son of a minister who “died by suspending himself,” 28 he prefigured his vacillating diversity by painting pictures, playing the organ, and inventing thirty different ways of flying. At Oxford he took to chemistry, serving as assistant to Robert Boyle. In 1662 he was appointed “curator of experiments” for the Royal Society; in 1665 he was professor of geometry in Gresham College; in 1666, after the Great Fire of London, he took to architecture and designed several major buildings—Montagu House, the College of Physicians, and Bethlehem Hospital (“Bedlam”). After long poring through microscopes, he published his chef-d’oeuvre, Micrographia, (1665), containing a number of suggestive ideas in biology. He proposed a wave theory of light, helped Newton in optics, and anticipated both the law of inverse squares and the theory of gravitation. He discovered the fifth star in Orion, and made the first attempts to determine by telescope the parallax of a fixed star. He propounded a kinetic theory of gases in 1678, and described a system of telegraphy in 1684. He was among the first to apply the spring to regulate watches; he laid down the principle of the sextant for measuring angular distances; he made a dozen scientific instruments. He was probably the most original mind in all that galaxy of geniuses that for a time made the Royal Society the pacemaker of European science; but his somber and nervous nature kept him from the acclaim that he deserved.

  Even in geology he had his moment of truth. He argued that fossils proved for the earth and for life an antiquity quite incompatible with the Book of Genesis; and he foresaw that the chronology of terrestrial life would someday be calculated from the differing fossils of successive strata. Most seventeenth-century writers still accepted the Biblical account of Creation, and some of them struggled to reconcile Genesis with the sporadic discoveries of geology. In An Essay towards a Natural History of the Earth (1695) John Woodward, after long study of his large collection of fossils, restored Leonardo da Vinci’s interpretation of them as the relics of plants or animals that had once lived on the earth, but even he thought that the distribution of fossils was a result of Noah’s Flood. An Anglican clergyman, Thomas Burnet, proposed (1680) a reconciliation between Genesis and geology by stretching the “days” of the Biblican Creation myth into epochs; this subterfuge proved acceptable; but when Thomas, gathering courage, went on to explain the story of Adam’s fall as an allegory, he found himself barred from ecclesiastical advancement.

  Athanasius Kircher was both a good Jesuit and a great scientist; we shall find him brilliant in a dozen fields. His Mundus subterraneus (1665) charted ocean currents, suggested that underground streams were fed from the sea, and ascribed volcanic eruptions and hot springs to subterranean fires; this seemed to confirm the popular belief that hell was in the center of the earth. Pierre Perrault (1674) rejected the idea that springs and rivers have subterranean sources, and upheld the now accepted view that they are the product of rain and snow. Martin Lister explained volcanic eruptions as due to the heating and consequent explosion of the sulphur in iron pyrites; and experiment showed that a mixture of iron filings, sulphur, and water, buried in the earth, became heated, cracked the earth above it, and burst into flames.

  The most prominent figure in the geology of this age was known to Denmark as Niels Stensen, and to the international of science as Nicolaus Steno. Born in Copenhagen, he studied medicine there and in Leiden, where he numbered Spinoza among his friends. 29 Migrating to Italy, he accepted Catholicism and became court physician to Ferdinand II at Florence. In 1669 he published a small volume, De solido intra solidum naturaliter contento, which one student has ranked as “the most important geological document of that century.” 30 Its purpose was to confirm the new view of fossils; but as a prelude Steno for the first time formulated principles to explain the evolution of the earth’s crust. Studying the geology of Tuscany, he found six successive strata. He analyzed their structure and contents, the formation of mountains and valleys, the causes of volcanoes and earthquakes, and the fossil evidence for formerly higher levels of rivers and the sea. The reputation earned by this book, and by Steno’s anatomical studies, led King Christian IV to offer him the chair of anatomy in the University of Copenhagen. He accepted, but his zealous Catholicism caused some friction; he returned to Florence, passed from science to religion, and ended as bishop of Titopolis and vicar apostolic for north Europe.

  Meanwhile geography was growing, usually as a by-product of missionary, military, or commercial enterprise. The Jesuits were almost as devoted to science as to religion or politics; many of them belonged to learned societies, which welcomed their geographical and ethnographical reports. As missionaries they ventured into Canada, Mexico, Brazil, Tibet, Mongolia, China . . . They gathered and remitted much useful knowledge, and made the best maps of the areas they visited. In 1651 Martino Martini published his Atlas sinensis, the fullest geographical description of China yet printed; and in 1667 Athanasius Kircher issued a magnificent China illustrata. Louis XIV sent six Jesuit scientists, equipped with the latest instruments, to map China again; in 1718 they issued a vast map in 120 sheets, covering China, Manchuria, Mongolia, and Tibet; this remained for two centuries the basis of all later maps of those areas. The cartographical wonder of the age was the map, twenty-four feet in diameter, which Giovanni Cassini and his aides drew in ink on the floor of the Paris observatory (c. 1690), showing the precise location, in latitude and longitude, of all important places on the earth. 31

  Some famous travelers belong to this period. We have already helped ourselves to Tavernier’s Six Voyages through Europe into Asia (1670), and Chardin’s Travels in Persia (1686). “In my six voyages,” wrote Tavernier, “and traveling by different roads, I had the leisure and opportunity to see all Turkey, all Persia, and all India. . . . The last three times I went beyond Ganges to the island of Java, so that for the space of forty years I have traveled above sixty thousand leagues by land.” 32 Chardin in one sentence anticipated Montesquieu’s Spirit of Laws: “The climate of each particular race is . . . always the primary cause of the inclinations and customs of its people.” 33 In 1670–71 François Bernier published an account of his travels and studies in India, and was accused of having shed his Christianity en route. 34 William Dampier buccaneered in a hundred lands and seas, wrote A New Voyage round the World (1697), and gave a cue to Defoe by telling how, on one of his later sallies, he piloted the vessel that rescued Alexander Selkirk from an otherwise uninhabited island (1709).

  Geography played its part in the erosion of Christian theology. As accounts of other continents accumulated, the educated classes of Europe could not but marvel at the variety of religious beliefs on the earth, the similarity of religious myths, the confidence of each cult in the truth of its creed, and the moral level of Mohammedan or Buddhist societies that in some respects shamed the gory wars and murderous intolerance of peoples dowered with the Christian faith. Baron de Lahontan, traveling in Canada in 1683, reported that he had much difficulty in meeting criticisms of Christianity by Indian natives. 35 Bayle again and again quoted the customs and ideas of the Chinese or the Japanese in criticizing European beliefs and ways. The relativity of morals became an axiom of eighteenth-century philosophy; one wit described the travels of Jacques Seden the hermaphrodite, who, to his delight, found a country where all the inhabitants were homosexuals, who looked upon Europe’s heterosexuals as immoral and disgusting monstrosities. 36

  V. PHYSICS

  Physics and chemistry conflicted less visibly than geography and biology with the ancient creed, for they dealt with solids, liquids, and gases that apparently had no connection with theology; but even in that material realm the progress of science was enlarging the rule of law, and weakening the faith in miracles. The study of physics rested on no philosophical interests, but on commercial and
industrial needs.

  Navigators, having induced astronomers to chart the skies more accurately, now offered rewards for a clock that would aid in finding longitude despite the perturbations of the sea. Longitude at sea could be determined by comparing the moment of sunrise or meridian with the time shown at that instant by a clock set to keep Greenwich or Paris time; but unless the clock was accurate the calculation would be dangerously wrong. In 1657 Huygens contrived a reliable clock by attaching a pendulum to a toothed escapement wheel, but such a clock was useless on a rolling and pitching ship.* After many trials, Huygens constructed a successful marine clock by substituting for the pendulum a balance wheel worked by two springs. This was among the illuminating suggestions expounded by him in one of the classics of modern science, the Horologium oscillatorium (The Pendulum Clock) published in Paris in 1673. Three years later Hooke invented the anchor escapement of clocks, applied spiral springs to the balance wheel of watches, and expounded the action of the springs on the principle Ut tensio sic vis—“As the tension, so the force”; this is still called Hooke’s law. Pocket watches could now be made more competently and cheaply than before.

  In the Horologium and a special monograph Huygens studied the law of centrifugal force—that every particle of a rotating body not lying in the axis of rotation is subject to a centrifugal force which increases with its distance from the axis, and with the speed of rotation. He set a clay sphere rotating rapidly, and found that it assumed the form of a spheroid flattened at both ends of the axis. On this centrifugal principle he explained the polar flattening of the planet Jupiter, and by analogy he concluded that the earth too must be slightly flattened at the poles.

  Huygens’ Tractatus de Motu Corporum ex Percussione (1703), published eight years after his death, continued the studies of Galileo, Descartes, and Wallis on the problems of impact. These presented intriguing mysteries, from the play of billiards to the collision of stars. How is force transmitted from a moving object to an object that it strikes? Huygens did not solve the mystery, but he stated some basic principles:

  I. If upon a body at rest another body equal to it impinges, the latter will come to rest after the impact, while the body initially at rest will acquire the velocity of the impinging body.

  II. If two equal bodies collide with unequal velocities, they will move, after impact, with interchanged velocities. . . .

  XI. In the mutual impact of two bodies the sum of the products of the masses into the squares of the relative velocities is the same before and after impact.

  These propositions, formulated by Huygens in 1669, gave partial expression to the most comprehensive principle of modern physics, the conservation of energy. They were, however, only ideally true, since they assumed complete elasticity in bodies. As no body in nature is perfectly elastic, the relative velocity of impinging objects is diminished according to the substance of which they are composed. Newton determined this rate of diminution for wood, cork, steel, and glass in the introductory scholium to Book I of his Principia (1687).

  Another line of investigation flowed from the experiments of Torricelli and Pascal on atmospheric pressure. Pascal had announced in 1647 that “any vessel, however large, can be made empty of all matter known in nature and perceptible to the senses.” 37 For hundreds of years European philosophy had proclaimed that natura abhorrat vacuum; even now a Paris professor informed Pascal that the angels themselves could not produce a vacuum, and Descartes scornfully remarked that the only existing vacuum was in Pascal’s head. But about 1650 Otto von Guericke constructed at Magdeburg an air pump which produced so nearly complete a vacuum that he astonished the dignitaries of his country, and the luminaries of the scientific world, with a famous experiment known as “the Magdeburg hemispheres” (1654). In the presence of the Emperor Ferdinand III and the Imperial Diet at Ratisbon, he brought two bronze hemispherical shells together in such a way that they were hermetically sealed but not mechanically connected at their edges; he pumped nearly all the air from their united interiors; then he showed that the combined strength of sixteen horses—eight pulling in one direction, eight in the opposite direction—could not separate the two halves of the sphere; but when a stopcock in one hemisphere was opened, admitting air, the shells could be separated by hand.

  Guericke had a flair for making physics intelligible to emperors. By emptying a copper sphere of water and air he caused it to collapse with a loud and startling noise; so he demonstrated the pressure of the atmosphere. He balanced two equal globes, and made one fall by pumping air from the other; so he proved that air has weight. He confessed that all vacuums were incomplete, but he showed that in his imperfect vacuums a flame would be extinguished, animals would suffocate, and a striking clock would make no sound; so he prepared for the discovery of oxygen, and revealed air as the medium of sound. He used the suction of a vacuum to pump water and raise weights, and shared in preparing for the steam engine. Having become burgomaster of Magdeburg, he delayed publishing his discoveries till 1672; but he communicated them to Kaspar Schott, Jesuit professor of physics at Würzburg, who printed an account of them in 1657. It was this publication that stimulated Boyle to the researches leading to the law of atmospheric pressure.

  Robert Boyle was a prime factor in the flowering of English science in the second half of the seventeenth century. His father, Richard Boyle, Earl of Cork, had acquired a large estate in Ireland, and Robert inherited most of this at the age of seventeen (1644). On frequent visits to London he became acquainted with Wallis, Hooke, Wren, and other members of the “Invisible College.” Fascinated by their work and their aspirations, he moved to Oxford and built a laboratory there (1654). He was a man of warm enthusiasms and of a piety that no science could destroy. He refused to communicate further (through Oldenburg) with Spinoza when he learned that the philosopher worshiped “substance” as God; but he placed much of his fortune at the service of science, and helped many friends. Tall and lean, frail and often ill, he held death at a distance by resolute diet and regimen. He found in his laboratory “that water of Lethe which causes me to forget everything but the joy of making experiments.” 38

  Having read of Guericke’s air pump, Boyle devised, with Hooke’s help (1657), a “pneumatic engine” to study the properties of the atmosphere. With this and later pumps he proved that the column of mercury in a barometer is supported by atmospheric pressure, and he measured roughly the density of the air. He advanced upon Galileo’s alleged experiment at Pisa by showing that even in an incomplete vacuum a bunch of feathers fell as rapidly as a stone. He showed that light is not affected by a vacuum, and therefore does not, like sound, use air as its medium of transmission; and he confirmed Guericke’s demonstration that air is indispensable to life. (When a mouse fainted in the vacuum chamber he stopped the experiment and revived it by letting in air.) We see the international of science in action when we learn that Guericke was stimulated by Boyle’s work to contrive a better air pump and resume his scientific studies; and that Huygens, visiting Boyle in 1661, was led to make similar instruments and tests.

  Boyle went on to creative inquiries into refraction, crystals, specific gravities, hydrostatics, and heat. He crowned his contributions to physics by formulating the law that bears his name: that the pressure of air or any gas varies inversely as its volume—or that at a constant temperature the pressure of a gas, multiplied by its volume, is constant. He first announced this principle in 1662, and generously credited it to his pupil Richard Towneley. Hooke had reached the same formula in 1660 by independent experiments, but did not make it known till 1665. A French priest, Edme Mariotte, about the same time as Boyle, arrived at a similar conclusion—“air is compressed according to the weight acting upon it”; he published this in 1676; and on the Continent his name, rather than Boyle’s, is attached to the law of atmospheric pressure. Whatever its parentage, it was one of the progenitors of the steam engine and the Industrial Revolution.

  Boyle and Hooke followed up Bacon’s view tha
t “heat is a motion of expansion not uniformly of the whole body, but in the smaller parts of it.” 39 Describing heat as “a property arising in a body from the motion or agitation of its parts,” Hooke distinguished it from fire and flame, which he attributed to the action of air on heated bodies. “All bodies,” said Hooke, “have some degree of heat in them,” for “the parts of all bodies, though never so solid, do yet vibrate”; 40 cold is merely a negative conception. Mariotte amused his friends by showing that “cold” could burn: with a concave slab of ice he focused sunlight upon gunpowder, causing it to explode. Spinoza’s friend Count Ehrenfried Walter von Tschirnhaus melted porcelain and silver dollars by focusing upon them the light of the sun.

  In the physics of sound two Englishmen, William Noble and Thomas Pigot, separately showed (c. 1673) that not only the whole, but different parts of a string may vibrate with diverse overtones, in sympathy with a near and related string plucked, struck, or bowed. Descartes had suggested this to Mersenne, and Joseph Sauveur, working on this idea, arrived independently at results similar to those of the Englishmen (1700); we should note in passing that Sauveur, who first used the word acoustics, had been a deaf mute from infancy. 41 In 1711 John Shore invented the tuning fork. Attempts to find the velocity of sound were made in this period by Borelli, Viviani, Picard, Cassini, Huygens, Flamsteed, Boyle, Halley, and Newton; Boyle, reckoning it at 1,126 feet per second, came closest to our current estimate. William Derham pointed out (1708) that this knowledge could be used to calculate the distance of a storm by observing the time interval between the lightning flash and the thunderclap.