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191 [293] KANT
LE GENTIL [295] for a great skill that not all chemists pos sessed. It was rendered obsolete by the invention of the system of spectral analy sis by Kirchhoff [648]. [293] KANT, Immanuel German philosopher
(now Kaliningrad, Soviet Union), April 22, 1724
1804
Kant, the son of a saddlemaker of Scottish descent, spent all his life in his obscure home town, never traveling more than sixty miles from it in his eighty years of life, following a regime so time-bound that his neighbors could almost set their clocks by him. He is best known as a profound phi losopher and as the author of Critique of
prehensive scheme of philosophy of most Teutonic thoroughness. In his youth, however, he had studied mathematics and physics at the University of Königs berg and in 1755, the year he obtained his doctor’s degree, he had published his physical view of the universe in General History of Nature and Theory of the Heavens. This book contained three important anticipations. First, he described the neb ular hypothesis, anticipating Laplace [347], Second, he suggested the Milky Way was a lens-shaped collection of stars and that other such “island uni verses” existed, an anticipation of Her- schel [321] and of twentieth-century as tronomy. Finally he suggested that tidal friction slowed the rotation of the earth, a suggestion that was correct but could not be demonstrated for another century. In 1770 he became professor of math ematics at the University of Königsberg, but in 1797 he shifted his attention to metaphysics and to logic. His daring speculations were made possible by the fact that he was patronized and pro tected by the freethinking Frederick II of Prussia. After Frederick’s death, Kant had to be more cautious. [294] MICHELL, John (mich'el) English geologist Born: Nottinghamshire, 1724 Died: Thornhill, Yorkshire, April 21, 1793 Michell obtained a master’s degree at Cambridge in 1752. He was appointed rector of St. Michael’s Church in Leeds and held the post till his death. He presented solid reasons for think ing the stars were light-years distant in 1784, half a century before Bessel [439] and others demonstrated the fact. He also preceded Herschel [321] in suspect ing the existence of binary stars. He invented a torsion balance similar to that which Coulomb [318] later in vented. With it he was going to measure the strength of the gravitational constant, but he died before he had the chance and it was Cavendish [307] who carried it through. Michell is remembered for another ac complishment. In 1760, five years after an earthquake at Lisbon that was so sud den and destructive that Europe was nearly panicked, Michell suggested that earthquakes set up wave motions in the earth. He noted the frequency of earth quakes in the vicinity of volcanoes and suggested that the quakes started as the result of gas pressure produced by water boiling through volcanic heat. He felt that earthquakes might start under the ocean floor and argued that the Lisbon earthquake was an example of that. He further pointed out that by noting the time at which the motions were felt, one could calculate the center of the earth quake. A century and a quarter later, this was brought to pass by Milne [814], Michell is rightly considered the father of seismology. [295] LE GENTIL, Guillaume Joseph Hyacinthe Jean Baptiste (luh- zhahn-teel') French astronomer Born: Coutances, Manche, Sep tember 12, 1725 Died: Paris, October 22, 1792 192 [296] DESMAREST HUTTON
Le Gentil, the son of a good-family- come-down-in-the-world, studied theol ogy at the University of Paris and grew interested in astronomy there. Soon, he involved himself in work at the Paris Observatory, and the stage was set for an almost unbelievable set of astro nomical misfortunes. He was commissioned to go to India in order to observe the transit of Venus in 1761. He was to view it from Pon dicherry on India’s southeastern coast. The Seven Years’ War was raging and Great Britain was fighting France in India. Just as Le Gentil reached India he found the British had taken Pondicherry and he was forced to remain on board ship during the transit. No decent obser vations were possible. However, another transit was due in 1769. There were no airplanes then and Le Gentil did not wish to go back to France and then back to India in long, long voyages on the miserable ships of the day. He decided to remain in India for eight years. There were no electric communications in those days and no easy way to inform the people back home of this decision. In 1769, he had to choose between Manila and Pondicherry for the observa tion. He decided on Manila but Pon dicherry was again a French possession land political decisions on the spot forced him to remain there. Came the crucial day: In Manila, the sun shone out of a cloudless sky. In Pondicherry, where Le Gentil was observing, clouds obscured the sun just during the time of transit. He returned to France to find himself considered dead and his heirs in posses sion of his property. —Oh, well, he straightened things out as best he could, married, had a daughter, and wrote a monumental and highly regarded two- volume book on India, so all was not lost.
[296] DESMAREST, Nicolas (day-muh- restO
French geologist Bom: Soulaines, Aube, Septem ber 16, 1725 Died: Paris, September 28, 1815 Just before the French Revolution, Desmarest, the son of a schoolteacher, was appointed inspector general and di rector of manufactures of France. As a royal appointee, he could not help but be under suspicion, and at the worst of the eventual Terror he was imprisoned. He survived, however, to be recalled to gov ernment service. A contemporary of Hutton [297], Des marest dealt with changes on the earth’s surface in similar fashion. Desmarest was the first to maintain that valleys had been formed by the streams that ran through them. He also carried forward Guettard’s [287] ideas, maintaining that basalt was volcanic in origin and that large sections of France’s rocks, for in stance, consisted of ancient lava flows. Unfortunately, A. G. Werner’s [355] er roneous theories that almost all rocks were formed by sedimentation from water held sway for a while, though the volcanic theories of Guettard and Des marest eventually won out. [297] HUTTON, James Scottish geologist Born: Edinburgh, June 3, 1726 Died: Edinburgh, March 26, 1797
Hutton, the son of a merchant, was left fatherless at three. He became a law yer’s apprentice, but grew interested in chemistry and returned to school to study medicine. He obtained his medical degree at Leiden in 1749, but he never practiced. Instead, he worked on various agricultural projects and set up a factory to manufacture ammonium chloride. From chemistry he went on to miner alogy and geology, interest in which was stimulated by his journeys on foot to different parts of England. Hutton’s in terest in this direction, which was heart ily encouraged by his good friend Black [298] , absorbed him more and more and in 1768 he retired on the proceeds of his factory and devoted himself to geology. By that time he had already founded the science, for until then geology did not really exist as an organized field of
[297] HUTTON
BLACK [298] study. Isolated scholars such as Steno [225] and Buffon [277] had speculated on the past history of the earth and com mented on rock strata, but there were no overall generalizations in the subject. A strong inhibiting factor was the conven tional belief in an earth created six thou sand years before according to the de scription in the Book of Genesis. Any countering argument seemed irreligious and offended the more conservative. Hutton’s careful studies of the earth’s terrain convinced him—as it had con vinced others before him—that there was a slow evolution of the surface structure. Some rocks, it seemed clear to him, were laid down as sediment and compressed; other rocks were molten in the earth’s interior and were then brought to the surface by volcanic ac tion; exposed rocks were worn down by wind and water. His great intuitive addition to all this was the suggestion that the forces now slowly operating to change the earth’s surface had been operating in the same way and at the same rate through all earth’s past. This is the “uniformitarian principle” and it was countered by those like Bonnet [291] who maintained that the history of the earth was one of sharp, catastrophic changes (“catas- trophism”). He also felt that the chief agent at work here was the internal heat of the earth. The planet, in short, was a gigan tic “heat-engine,” a not-unnatural con clusion, perhaps, for one who was a friend of Watt [316] as well as of Black. To Hutton it seemed as though the earth’s history must be indefinitely long, since, although the actions involved were creepingly slow, vast changes had never theless had time to take place. There seemed no sign of a beginning, he wrote, and no prospect of an end. Hutton summarized his views in a book called Theory of the Earth, pub lished in 1785. Since it first advanced the general principles upon which geology is now based, he is often called the “father of geology.” In the book Hutton also dealt with rainfall and reached essen tially modern conclusions, to wit: the amount of moisture that the air could hold rose with temperature. Conse quently when a warm air mass met a cold one so that the temperature of the former dropped, some of the moisture could no longer be held in vapor form and precipitated as rain. Hutton’s geological views met with strong resistance and objection from those who held to the biblical account of creation. It was the time of the French Revolution and England was going through a strong conservative reaction. Anything smacking ever so faintly of going against establishment views was suspect. It was not until the popularizing work of Lyell [502] a half century later and well after Hutton’s death that the view of the Theory of the Earth came into its own. At the time of his death, Hutton was working on a book in which he ex pressed a belief in evolution by natural selection, a view to be made famous by Charles Darwin [554] six decades later. However, Hutton’s manuscript was not examined till 1947, so that his antici pation of Darwin remained unsuspected for a century and a half. [298] BLACK, Joseph Scottish chemist Born: Bordeaux, France, April 16, 1728 Died: Edinburgh, December 6, 1799
Black’s father, a Scots-Irish wine mer chant living in France, sent young Jo seph (one of thirteen children) back to the British Isles in 1740 for his educa tion. Black studied medicine at Glasgow, then, after 1750, at Edinburgh and even tually held professorial positions at each of these institutions and proved an excel lent and popular lecturer. While still a medical student he grew interested in kidney stones and from these moved on to minerals that were similar. His thesis for his medical degree—obtained in 1754—proved to be a classic in chemis try. The work was published in 1756 (the year in which he became professor of chemistry at Glasgow) and in it Black reported that the compound we now call 194 [298] BLACK
BLACK [298] calcium carbonate was converted to cal cium oxide upon strong heating, giving off a gas that could recombine with the calcium oxide to form calcium carbonate again. Black called the gas “fixed air” because it could be fixed into solid form again. We call it carbon dioxide. Carbon dioxide was studied by Hel mont [175] a century and a quarter be fore, but Black was the first who showed that it could be formed by the decom position of a mineral as well as by com bustion and fermentation. Furthermore, by involving a gas in a chemical reaction he divested it of its mystery and made it not so very different, from the stand point of chemistry, from liquids and solids. And since calcium oxide could be converted to calcium carbonate simply by exposure to the air, it followed that carbon dioxide was a normal component of the atmosphere. He also recognized the existence of carbon dioxide in ex pired breath. In studying the properties of carbon dioxide, Black found that a candle would not bum in it. A candle burning in ordi nary air in a closed vessel would go out eventually and the air that was left would no longer support a flame. This might seem reasonable since the burning candle formed carbon dioxide. However, when the carbon dioxide was absorbed by chemicals, the air that was left and was not carbon dioxide would still not support a flame. Black turned this prob lem over to Daniel Rutherford [351], his young student, and within a decade chemistry was in part revolutionized by just such experiments. In studying the effect of heat on cal cium carbonate, Black measured the loss of weight involved. He also measured the quantity of calcium carbonate that would neutralize a given quantity of acid. This technique of quantitative measurement, as applied to chemical re actions, was to come into its own a few decades later with Lavoisier [334]. Black’s work in physics was equally important. In 1764 he grew interested in the phenomenon of heat and was the first to recognize that the quantity of heat was not the same thing as its inten
sured as temperature. Thus, he found that when ice was heated, it slowly melted but did not change in tempera ture. Ice absorbed a quantity of “latent heat” in melting, increasing the amount of heat it contained but not the intensity. An even larger quantity of latent heat was involved in the conversion of water to vapor by boiling. Furthermore, when water vapor con densed to water, or when water froze to ice, an amount of heat was given off equal to that taken up by the reverse change. Yet the act of condensation or freezing involved no temperature change either. The fact that the heat taken up in one change was given off in the reverse change was a step in the direction of un derstanding the great generalization called “conservation of energy,” which was to be clearly established some three quarters of a century later with the work of such men as Mayer [587], Joule [613], and Helmholtz [631]. The heat taken up by water in boiling was a clue to the far greater energy con tent of steam at the boiling point temper ature as compared with an equal weight of liquid water at the same temperature. This fine theoretical point was known to James Watt [316], who was aware of Black’s work, and Watt used it in de veloping his steam engine. (It is never sufficiently realized, particularly in the United States, how much the “down-to- earth” inventor is indebted to the “ivory tower” theoretician.) Black also showed that when equal weights of two different substances at different temperatures are brought to gether and allowed to come to tempera ture equilibrium, the final temperature is not necessarily at the midway point. One substance might lose 30°, for instance, while the second was gaining only 20°. The same quantity of heat, in other words, might effect a temperature change 50 percent greater in one sub stance than in another. This charac teristic temperature change resulting from the input of a particular amount of heat is now called the specific heat. Black had trouble accounting for all this. He, in common with other chemists of his time, believed heat to be an im 195 [299] LAMBERT
COOK [300] ponderable fluid, like light, electricity, or the phlogiston postulated by Stahl [241]. In terms of an imponderable fluid pour ing from one substance to another, the concept of specific heat and latent heat could be explained only by troublesome and implausible arguments. When the ki netic theory of heat was finally devel oped by men such as Maxwell [692], Black’s experiments fell neatly into place.
[299] LAMBERT, Johann Heinrich (lahm'behrt) German mathematician
26, 1728 Died: Berlin, September 25, 1777 Lambert was the son of a poor tailor. He had to quit school at twelve to help his father and was forced thereafter to scrimp what education he could out of life. Fortunately, men of great talent can make do even under difficulties. He began to earn his living as a tutor until he attracted the attention of Frederick II of Prussia who saw to it, in 1764, that the final decade of his life was passed in reasonable comfort. In mathematics Lambert, in 1768, proved pi to be an ir rational quantity (though a century later Lindemann [826] was to give it an even more subtle distinction) and introduced hyperbolic functions into trigonometry. In 1760 he published his investigations of light reflection. His book was in Latin and his word for the fraction of light reflected diffusely by a body was albedo (“whiteness”). The term is still com monly used in astronomy to represent the reflectivity of planetary bodies. He was the first to devise methods for mea suring light intensities accurately, and the unit of brightness is the lambert, in his honor. In 1761 he speculated that the stars in the neighborhood of the sun made up a connected system and that groups of such systems made up the Milky Way. He suspected that there might be other conglomerations like the Milky Way in the far reaches of space. The accuracy of his guesses was con
firmed by the careful work of Herschel [321] a generation later. [300] COOK, James English navigator
Yorkshire, October 27, 1728 Died: Kealakekua Bay, Hawaii, February 14, 1779 Cook’s reputation as a seaman is proved by the fact that he is hardly known by any name other than Captain Cook. His first name is all but forgot ten. He was the son of a farmhand and his first job was in a haberdasher’s shop. While still young he was apprenticed to a firm of shipowners and worked his way up to mate. In 1755 he joined the Royal Navy and by 1759 had qualified as a master and took part in Wolfe’s expedi tion against Quebec in the French and Indian War. The expeditions in which he engaged were intended for sounding and survey ing, for gaining knowledge of the ocean and of the geographical nature of the earth. Thus he spent several years in the sixties surveying the coasts of Labrador and Newfoundland. He observed a solar eclipse on August 5, 1766, near Cape Ray, Newfoundland. He was the first of the really scientific navigators. In 1768 he made the first of three voy ages into the Pacific that were to make him the most famous navigator since Magellan [130], two and a half centuries earlier. Under the auspices of the Royal Society (through the Admiralty) he was sent to the South Pacific to observe the transit of Venus from the newly discov ered island of Tahiti. In the course of that expedition he discovered the Ad miralty Islands and the Society Islands, named for his sponsors. He also circum navigated New Zealand, explored its shores, and landed in Australia, being the first to gain a notion of the size and position of this last of the inhabited con tinents to be opened to the Europeans. Accompanying him as ship’s botanist was Banks [331]. In a second expedition, from 1772 to |
