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176 [270] LA CONDAMINE FRANKLIN
sinis were right, then the theory of uni versal gravitation was wrong. It became more and more important to check the matter. It was decided to survey regions of the earth accurately to determine differences in surface curvature. To get the greatest differences in curvature, one expedition under La Condamine was sent in 1735 to Peru, almost on the equator. Another expedition, under Maupertuis [267], was sent to Lapland in the far north of Sweden. These expeditions were gather ings of giants, for included were Bouguer [264], Clairaut [283], and others of like caliber. The results were quite conclusive. The earth’s curvature was distinctly higher at the equator than at the poles. The earth was therefore an oblate spheroid, bulging at the equator and flattened at the poles. Newton, as was to be expected, was right, while the Cassinis, as was even more to be expected, were wrong. La Condamine used his stay in South America to go off on an exploratory jaunt. He was the first European to ex plore the Amazon territory with any thoroughness, and he sent home quanti ties of a peculiar tree sap called caou tchouc, thus introducing what we now call rubber to Europe. He also discov ered and brought back curare, the origi nal of the mysterious South American poisons so beloved by mystery writers, which, however, is also used clinically as a muscle relaxant. The expeditions to Peru and Lapland had made it quite plain that the delicate measurements being undertaken in the eighteenth century were being hampered by the lack of internationally accepted standard units of measure. La Conda mine was in the forefront of the fight to establish such a system of measure but did not live long enough to see it ac complished in the 1790s, with the intro duction of the metric system. He was also one of those who speculated on the feasibility of inoculation against small pox but died twenty-two years before Jenner [348] introduced such inoculation successfully. [271] CELSIUS, Anders (sel'see-us) Swedish astronomer Born: Uppsala, November 27, 1701
Died: Uppsala, April 25, 1744 Celsius was of a famous scientific fam ily. His father and grandfather were mathematicians, his uncle a botanist. He studied the aurora borealis and, in his re port in 1733, was the first to associate it with changes in the earth’s magnetic field. He also took part in the expedition to Lapland under Maupertuis [267]. In 1730 he became professor of as tronomy at Uppsala and in 1740 was placed in charge of a large new observa tory there, which, however, he was not to enjoy for long, for he died at an early age. He was the first to try to determine the magnitude of stars by measuring the intensity of their light by a device other than the human eye. His greatest accomplishment, as it happened, had nothing to do with as tronomy. It concerned the temperature scale he devised, which divided the tem perature difference between the boiling point and freezing point of water into an even hundred degrees. He first described this in 1742 when he placed the boiling point at 0° and the freezing point at 100°, but the next year this was re versed. This is the centigrade scale (“hundred steps”) and is used by scien tists everywhere. In 1948 it was decided by general agreement to begin to refer to it as the Celsius scale. [272] FRANKLIN, Benjamin American statesman and scientist
January 17, 1706 Died: Philadelphia, Pennsylvania, April 17, 1790 Benjamin Franklin was the fifteenth child of seventeen, born to a poor can- dlemaker. He was printer, writer, politi cian, diplomat, and scientist, quite a phe nomenon in the New World in the eigh teenth century, yet he only had two years of formal schooling. He was the only
[272] FRANKLIN
FRANKLIN [272] American of colonial days to achieve a European reputation. He is best known to Americans, of course, as one of the founding fathers of the nation, but his fame in his own time, at least in Europe, was that of a natural philosopher. He founded America’s first scientific society, the American Philosophic Society, in 1743.
His ingenuity showed itself in nu merous inventions, notably the Franklin stove and bifocal glasses. However, it was in the field of electricity that he achieved his greatest results. Static electricity had become a fas cinating toy in the century since Guericke [189] had produced the first electric machine and Musschenbroek [257] his Leyden jar in 1745. The latter was actually a “condenser,” a name coined by Volta [337] a half century later. It could store large quantities of static electric charge poured into it from a machine in which the charge was pro duced through friction. The Leyden jar could then be discharged when a hand was brought near the center rod, and if enough electricity had been stored in the first place, the owner of the hand would be given a shock he was not likely to forget. If the jar was brought near metal, a tiny jagged spark would leap across the air gap and this would be accompanied by a sharp crackle. Many scientists were experimenting with Leyden jars, and Franklin was one of them. He noted the spark of light and the crackle and wondered whether these might not be a very miniature lightning and thunder. Or perhaps, looking at it from another standpoint, might not the majestic thunder and lightning of the heavens be but the interplay of elec tricity, with earth and sky making up the halves of a gigantic planetary Leyden jar? Benjamin Franklin decided to attempt an experiment—one for which he lives dramatically in the minds of posterity. He flew a kite in a thunderstorm in 1752. The kite carried a pointed wire to which Franklin had attached a silk thread that could be charged by the elec tricity overhead; that is, if there was electricity overhead. As the storm clouds gathered and lightning flickered, Franklin put his hand near a metal key tied to the silk thread and the key sparked just as a Leyden jar would have. Moreover, Franklin charged a Leyden jar from the key just as easily as he would have from a man-made elec trical machine. Franklin’s kite electrified the scientific world, and he was made a member of the Royal Society. Franklin’s luck was extreme, for the experiment is a killer. The next two men who tried to duplicate his feat were both killed. (At about the same time, how ever, Canton [290], in observations that involved no danger, pointed up another and more subtle connection between electricity and the sky.) Franklin was able to put his experi ment to practical use at once. His experi mentation with the Leyden jar had shown him as long before as 1747 that it discharged more readily and over greater gaps of air if it came near a pointed sur face. It was as if the pointed surface at tracted the electricity. Franklin therefore suggested that pointed metal rods be placed above the roofs of buildings, with wires leading to the ground. Such light ning rods would discharge the clouds safely and protect the buildings them selves. They did indeed prove efficacious and by 1782 there were four hundred lightning rods in use in Philadelphia alone. Franklin had averted the artillery of Zeus.
When a quarter century later the aged Franklin represented the infant United States during the Revolutionary War at the court of France, he proved the ideal man for the job. Not only did his care fully affected Republican simplicity per versely appeal to the aristocrats at Ver sailles, but it was the Age of Reason, and educated Frenchmen fell all over the man who had tamed the lightning of the sky and brought it to earth. How much of America’s successful birth can be traced back to a kite flying in a thunder storm?
Franklin also performed an inesti mable theoretical service to the science of electricity, with one accidental flaw. It was known that there were two kinds of electric charge. Two amber rods repelled 1 7 8
[272] FRANKLIN
DOLLOND [273] each other if both were rubbed and elec trified. Similarly two electrified glass rods repelled each other. An electrified amber rod, however, attracted an electrified glass rod. It seemed a case of “opposites attract and likes repel,” as in magnetism, where the north pole of a magnet at tracts the south pole of another, while two north poles repel each other and two south poles repel each other. Franklin reasoned that this could be explained by supposing electricity to con sist of a subtle fluid that could be present either in excess or in deficiency. Two substances containing an excess of the fluid repelled each other, as did two sub stances containing a deficiency. An ob ject with an excess, however, would at tract one with a deficiency; the excess would flow into the deficiency (over an air gap and accompanied by thunder and lightning sometimes) and the two elec trifications would be neutralized. Franklin suggested that an excess of the fluid be called positive electricity and a deficiency be called negative electricity. A century and a half after Franklin’s day, electricity came to be associated with subatomic particles, particularly with the electron, discovered by J. J. Thomson [869], However, if static elec tricity is considered an accumulation of electrons or a deficiency of them, the situation as we understand it today is ex actly what Franklin proposed. Unfortunately the objects Franklin guessed contained the excess of elec tricity actually contain a deficiency of electrons. (He took an even-money stab in the dark and missed.) The electrician in setting up his circuits even today as sumes that the electric current flows from the positive terminal to the nega tive, but the physicist knows that elec trons flow from the negative terminal to the positive. It doesn’t matter, however, which convention is followed as long as whoever is working with the circuit sticks to the same convention through out. Franklin’s busy mind concerned itself with other matters as well. While in France he watched with extreme interest the early attempts at ballooning and in volved himself in the medical theories of Mesmer [314], coming to some remark ably sound conclusions as to psycho neuroses as a result. He worked out (as well as he could) the course of storms over the North American continent and was the first to study the circulating belt of warm water in the North Atlantic that we now call the Gulf Stream. In 1900 Franklin was selected as one of the charter members of the Hall of Fame for Great Americans. [273] DOLLOND, John English optician Born: London, June 10, 1706 Died: London, November 30, 1761
Dollond was the son of a Huguenot refugee from France. (Louis XIV, be cause of his measures against the French Protestants in the 1680s, lost thousands of useful subjects to surrounding nations. Adolf Hitler was to make a similar mis take two and a half centuries later.) Dollond began work in his father’s trade of silk weaving but educated him self in his spare time, teaching himself Latin, Greek, mathematics, and science. In middle life he joined his own son in manufacturing optical instruments. Their work was unsurpassed until the time of Fraunhofer [450] over half a century later.
He followed the suggestions of David Gregory [240] and others and tried to develop lenses that in spite of Newton’s [231] theories would not show chromatic aberration. Actually this feat had been accomplished in 1733, it is now known, but the results had not been published. Even so, Dollond had to fight the matter through the courts before he was awarded a patent. In any case Dollond succeeded in 1758 and announced his results to the Royal Society, which awarded him the Copley medal and three years later elected him a member. In 1761 (the year of his death) he was even appointed optician to King George III. Dollond solved the problem by using two different kinds of glass, which re-
[274] CHÂTELET
EULER [275] fracted the various colors of light in different ways and combined them in such a fashion that the action of one glass just counterbalanced the action of the other. The invention of such an achromatic telescope kept the refracting instruments in the race with reflectors, though by the twentieth century the reflecting telescope was definitely the winner, thanks to the energy and enterprise of Hale [974]. Doflond’s work also led to the invention of achromatic microscopes, a more im portant consequence, for in microscopy there was no easy substitute for refrac tion. Furthermore Dollond showed that Newton was definitely wrong in his con tention that chromatic aberration could not be avoided, and it was a healthy thing for science to be shown that even Newton could be wrong. [274] CHÂTELET, Gabrielle Emilie le Tonnelier de Breteuil, marquise du (shah-tlayO French science writer Born: Paris, December 17, 1706 Died: Luneville, Meurthe-et- Moselle, September 10, 1749 Of noble birth, Gabrielle Emilie mar ried the marquis de Châtelet in 1725. She bore him three children, after which he grew quite serious about his military career and saw her but infrequently. She didn’t seem to take that much to heart but pursued her own life with the greatest of satisfaction. She had been well educated in all the subjects deemed necessary to a cultured existence, including science, and from 1733 on she established a liaison with the leading intellectual figure of the age, Voltaire [261]. She was also a close friend of Maupertuis [267] who taught her mathematics and who encouraged her to continue with her science educa tion and, later on, with Clairaut [283]. Because Voltaire was a great admirer of Newton [231], he urged the brilliant marquise to undertake the task of trans lating the Principia Mathematica from Latin into French. She began the task in 1745 and continued it till her death (in childbirth) and did a masterly job of it. Voltaire wrote a preface and it appeared, complete, in 1759. Since most of Europe’s intellectuals in those days could manage to make themselves understood in French and could read the language, her translation (still the only one in French) opened the meaning of the Newtonian universe to those continentals who were not at home in either Latin or English. [275] EULER, Leonhard (oiler) Swiss mathematician
tember 18, 1783 Euler, the son of a Calvinist minister who dabbled in mathematics, studied under the Bemoullis and was a friend of Daniel Bernoulli [268]. Euler received his master’s degree at sixteen from the University of Basel. When the Bernoullis went to St. Petersburg, Russia, they persuaded Euler (in 1727) to follow, for there the Em press Catherine I (widow of Peter the Great) had recently founded the Peters burg Academy and there he succeeded Bernoulli as professor of mathematics in 1733.
In St. Petersburg in 1735 Euler lost the sight of his right eye through too- ardent observations of the sun in an at tempt to work out a system of time de termination. In 1741, at a time when the young Ivan VI succeeded to the throne and times in Russia grew troubled, Euler went to Berlin. There he was to head and revivify the decaying Academy of Sciences, founded by Leibniz [233] at the invitation of the new king, Frederick II. He didn’t get along with Frederick, a king who demanded approval of his wretched poetry and who had no appre ciation for pure mathematics. Euler was remembered in Russia, however, and in 1760, during the Seven Years’ War, when Russian troops occupied Berlin, Euler’s house was given special protec tion. In 1766, at the invitation of the new 180 [275] EULER
LINNAEUS [276] empress, Catherine II (the Great), he re turned to St. Petersburg and remained there for the rest of his life. During his second stay in Russia he challenged the visiting Diderot [286] to a debate on atheism. Euler, a religious man who in his youth had contemplated entering the ministry like his father, advanced his own argument in favor of God in the form of a simple and completely irrele vant algebraic equation. Poor Diderot, who knew no mathematics whatever, was speechless. Feeling a fool, he left Russia. Euler was the most prolific mathe matician of all time, writing on every branch of the subject and being always careful to describe his reasoning and to list the false paths he had followed. He lost the sight of his remaining eye in 1766 but that scarcely seemed to stop him or even slow him down, for he had a phenomenal memory and could keep in mind that which would fill several blackboards. He published eight hundred papers, some of them quite long, and at the time of his death, left enough papers behind to keep the printing presses busy for thirty-five years. He applied his mathematics to astron omy, working out the nature of some perturbations, being in this respect the precursor of Lagrange [317] and Laplace [347]. He began to replace the geometric methods of proof used by Galileo [166] and Newton [231] with the algebraic, a tendency carried to its conclusion by Lagrange. In particular he worked on lunar theory, that is, on the analysis of the exact motion of the moon, the com plications of which have been the despair of astronomers and mathematicians since the time of Kepler [169]. Although his results were far from perfect, they repre sented an improvement on what had gone before. He also held that light was a wave form and that color depended on wave length. A generation later, Young [402] demonstrated this conclusively. Euler published a tremendously suc cessful popularization of science in 1768, one that remained in print for ninety years. He died shortly after working out certain mathematical problems in con nection with ballooning, inspired by the successful flight of the Montgolfier brothers [325]. He introduced the sym bol “e” for the base of natural log arithms, “i” for the square root of minus one, and “f() ” for functions. [276] LINNAEUS, Carolus (lih-nee'us) Swedish botanist Born: Sôdra, Råshult, Småland, May 23, 1707 Died: Uppsala, January 10, 1778 Linnaeus’ name is the Latinized form of Carl von Linné. As a child he seemed rather dull, but his father, a pastor, sent him to medical school, first at Lund, then at Uppsala, a bit against his will. Fortunately, put to the test, young Lin naeus made out well scholastically. Fi nancially, though, he came close to di saster at this time. Luckily for him, Cel sius [271], then teaching at Uppsala, took the young man into his home. Linnaeus had always been interested in plants and even as an eight-year-old he had gained the affectionate nickname of “the little botanist.” This interest contin ued at college and he studied, in particu lar, the stamens and pistils. Linnaeus wrote a paper on the subject and this led him to feel that he could in troduce a new and better classification of plants based on their sexual organs. In 1732 the University of Uppsala (where he was already lecturing on botany as Rudbeck [218] had done before him) asked him to visit Lapland to examine its flora. This he did, traveling forty-six hundred miles throughout northern Scandinavia, discovering a hundred new species of plants and carefully observing the animal life as well. His interest in sex led to an interesting by-product: he was the first to use the symbols $ and $ for “male” and “female.” He followed this up by traveling through England and west Europe. In 1735 Systerna Naturae was published. In this famous book Linnaeus established the classification of living things in a particularly methodical way, completely overshadowing the prior work of Ray
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