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271 [404] BIOT
BIOT [404] himself could scarcely have foreseen. It resulted from his rather routine investi gations of plant pollen. In 1827 as he was viewing a suspen sion of pollen in water under the micro scope, he noted that the individual grains were moving about irregularly. This, he thought, was the result of the life hidden within the pollen grains. However, when he studied dye particles (indubitably nonliving) suspended in water, he found the same erratic motion. This has been called Brownian motion ever since and Brown could merely re port on the observation. He had no ex planation for it. Nor had anyone else until the development of the kinetic theory of gases by men such as Maxwell [692] a generation later. It seemed plain, after Maxwell and es pecially after the work of Einstein [1064] and Perrin [990] a half century after Maxwell, that the Brownian motion was actually a visible effect of the fact that water was composed of particles. It was the first evidence for atomism that was primarily an observation rather than a deduction. [404] BIOT, Jean Baptiste (byoh) French physicist
Biot, the son of a treasury official, served a year in the artillery in 1792, fighting the British. Then he entered the ficole Polytechnique, studying under Lagrange [317] and Berthollet [346]. He and Malus [408] took part in a street riot in 1795, one which was easily put down, marking the end of the French Revolution. The man who put it down was Napoleon Bonaparte, who thus took the first step on his rise to prominence. Biot suffered imprisonment for a while as a result. In later life, he remained consistently anti-Napoleon and he was awarded the Legion of Honor by Louis XVIII who succeeded the fallen em peror.
Biot obtained an appointment as pro fessor of mathematics at the University of Beauvais, and in 1800 moved on to the Collège de France through the spon sorship of Laplace [347], whose self-cen tered soul he had pleased by offering to read proof on the colossal Mécanique
proved himself no disappointment in the post. In 1803 he investigated a reported sighting of material falling from heaven and his findings finally convinced a skep tical scientific world that meteorites existed. His first real fame, however, came not so much in science itself as in a stroke of adventure. In 1804 there seemed a heaven-sent opportunity to study the atmosphere with a balloon left over from Napoleon’s Egyptian campaign. Biot and Gay-Lus sac [420] loaded themselves down with instruments, plus an assortment of small animals, and made an ascension on Au gust 23, 1804, showing that terrestrial magnetism remained undiminished at the heights they reached. It was a tentative groping of science toward the upper at mosphere, a move that was to reach its climax in the rocketry of the mid-twen tieth century. Biot and Gay-Lussac ran a number of experiments and collected many observa tions between heights of one and three miles. The descent was dangerous and tricky and Biot panicked. Gay-Lussac made another ascension later in the year to a height of four miles but Biot did not accompany him. Biot and Arago [446] traveled to Spain in 1806 on a meridian-measuring expedi tion and remained close friends for a decade, until Thomas Young’s [402] sud den revival of the wave hypothesis of light threw the world of physics into tur moil. At first, both Arago and Biot strongly favored the old particle hypoth esis and Biot worked out an ingenious mathematical treatment of it that greatly pleased his old sponsor, Laplace. Arago, on the other hand, defected and became one of the prime movers in favor of the wave hypothesis. A bitter dispute arose between the two friends and they were friends no more. Biot’s most important work was in connection with what we now call po larized light. Bartholin [210] had discov
[405] BUCH
BAILY [406] ered the phenomenon of double refrac tion a century and a half before, and it was shown that the two rays of light that emerged from Iceland spar differed in properties, a difference that was usefully taken advantage of by Nicol [394]. This phenomenon could only be ex plained properly by a wave theory of light and Fresnel [455] produced such an explanation. However, one doesn’t have to explain a phenomenon to work with it, and though Biot did not accept Fres nel’s theories, he nevertheless worked fruitfully with polarized light. In 1815 he showed that organic sub stances might, in effect, rotate polarized light either clockwise or counterclock wise, when the organic compounds were liquid or in solution. He suggested that this was due to an asymmetry that might exist in the molecules themselves. By 1835 he showed how the hydrolysis of sucrose could be followed by changes in optical rotation, thus founding the sci ence of polarimetry. In 1840 he was awarded the Rumford medal. He lived long enough to see Pasteur [642] prove asymmetry in organic crys tals that had this twisting effect on po larized light, but (despite his longevity) not long enough to see the molecular asymmetry he had predicted become an important facet of organic chemistry through the work of Van’t Hoff [829] and Le Bel [787]. Though an atheist most of his adult life, he returned to Catholicism in 1846. [405] BUCH, Christian Leopold von (bookh)
German geologist Born: Stolpe, Prussia, April 25, 1774
Died: Berlin, March 4, 1853 Buch was one of thirteen children of a wealthy Prussian landowning family. He studied mineralogy and chemistry at Ber lin, and then went on to be a student of Werner [355] the great neptunist, from 1790 to 1793. Buch did not have to work for a living and engaged himself in traveling about Europe in order to study volcanic re gions, sometimes in the company of Humboldt [397], His studies quickly showed him that Werner’s theories were quite wrong and that they could only be held by someone who, like Werner, had never actually seen the volcanic regions he theorized about. For instance, Buch’s investi gations at the turn of the century and shortly after, showed that the Italian vol canoes rested on granite and there was no sign of any coal beds the burning of which, according to Werner, supplied the heat.
Instead, Buch became more and more certain that both basalt and granite were formed by volcanic action and had crys- talized out of the molten state rather than settling out of a watery suspension as Werner had claimed. In 1826 he pre pared a huge geologic map of Germany, the first of its kind. With Buch, vulcanism triumphed over neptunism, and the stage was set for the great geologic synthesis of Lyell [502]. [406] BAILY, Francis English astronomer
28, 1774 Died: London, August 30, 1844 Baily was a prosperous stockbroker who had received only an elementary ed ucation. He retired in 1825, at last able to devote himself to his intellectual mis tress, astronomy. He had been one of the founders of the Royal Astronomical So ciety and was a perennial president or vice president of the organization. On May 15, 1836, during an eclipse of the sun, he described an effect whereby just before the last glowing sliver of sun disappeared behind the moon, it broke into a line of shining bits and pieces, as the sunlight made its way between the jutting mountains on the moon’s horizon. The same phenomenon appeared on the other side when the sunlight first broke through between the mountains, then quickly joined into an intact curve of sun. The broken bits of sunlight are still called Baily’s beads. This discovery fired new astronomical
[407] AMPÈRE
AMPÈRE [407] interest in eclipses and began the custom of outfitting long-distance expeditions to observe eclipses in far comers of the world; something which has been going on ever since. [407] AMPÈRE, André Marie (ahm- pare')
French mathematician and physi cist
Born: Lyon, January 22, 1775 Died: Marseille, June 10, 1836 Young Ampère was privately tutored and proved to be quite a phenomenon, devouring the encyclopedic works of Bulfon [277] and Diderot [286] and mas tering advanced mathematics by the age of twelve. He even learned Latin in order to read the works of those like Euler [275] who wrote in that language. The even tenor of his youth was, how ever, intermpted by the coming of the French Revolution. In 1793 Lyon revolted against the rev olutionaries and was taken by the repub lican army. Ampère’s father, who was a well-to-do merchant and one of the city’s officials, was guillotined. Ampère went into a profound depression as a result, out of which, with the encouragement of the sympathetic Lalande [309], he strug gled with difficulty. In 1803 his beloved wife of but four years died and this again hit him hard. Indeed, he never recovered from that blow. (In 1818 he married a second time, and this time the marriage was unhappy.) At Napoleon’s insistence, Ampère con tinued a fruitful career as a professor of physics and chemistry at Bourg, and then in 1809 as a professor of mathe matics in Paris. He was, like Newton, the classic ex ample of an “absent-minded professor.” Many stories (not necessarily true) are told of him, including one in which he forgot to keep an invitation to dine with the Emperor Napoleon, probably the only occasion on which the emperor was ever disappointed in this manner—and with impunity, for Napoleon appointed him inspector general of the national university system in 1808. When the discovery of Oersted [352]—that a wire carrying an electric current deflected a compass needle—was announced to the French Academy of Sciences in 1820, French physicists burst into activity. (Nothing like it was seen until the announcement of nuclear fission a century later.) Ampère and Arago [417] were in the forefront. Within one week after Oersted’s work had been reported, Ampère showed that the deflection of the needle could be expressed by what is now known as the “right-hand screw rule.” The right hand is imagined as grasping the wire through which the cur rent runs, with the thumb pointing in the direction of the current. The fingers then indicate the direction in which the north pole of a magnet will be deflected. The magnet will be deflected in the direction of the curling fingers at any point around the wire, so that one might imag ine a magnetic force circling the wire. This was the beginning of the concept of lines of force that Faraday [474] was to generalize and that was eventually to ad vance the picture of the universe beyond the purely mechanical concepts of Gali leo [166] and Newton [231]. Of course, in setting up this right-hand screw rule, one had to decide in which direction the current was traveling. There was no clear indication of that from the wire itself. It was a matter of convention only whether the current was flowing from the positive pole to the negative pole or vice versa—at least this was true in Ampère’s time. It seemed natural to take the flow from positive to negative, using the concept of Franklin [272] that the positive pole had the ex cess of “electrical fluid” and the negative pole the deficiency. That convention has been used ever since, but Franklin had guessed wrong and Ampère had gone wrong with him. We now know that the electric current is a movement of electrons flowing from the negative pole to the positive. How ever, taking things in reverse does no damage as long as one remains consis tently wrong. Ampère showed that visualizing the at tractions and repulsions set up by a cur 2 7 4
[407] AMPÈRE
MALUS [408] rent-carrying wire did not require either a magnet or iron filings. He set up two parallel wires, one of which was freely movable back and forth. When both wires carried current in the same direc tion, the two wires clearly attracted each other. If the current flowed in opposite directions, they repelled each other. If one wire was free to rotate about an axis perpendicular to itself and to the other wire, then, when the currents flowed in opposite directions, the movable wire ro tated through a semicircle, coming to rest in such a position that the currents flowed in the same direction in both. Ampère also worked with the mag netic fields set up by currents flowing through a circular wire, and he recog nized, as did Arago, that from a theoret ical standpoint a helix of wires (a wire curved into bedspring shape) would be have as though it were a bar magnet. He called such a helix a solenoid. This no tion was put into practice by Sturgeon [436] and was then refined to a startling degree by Henry [503]. It was Ampère’s experiments that founded the science of electric currents in motion, which Ampère named elec trodynamics. He also introduced the term “electrostatics” for the older study of stationary electric charges in which Franklin’s work had been so important. Meanwhile, Oersted’s discovery had led to the quantization of electrical ex perimentation. If a magnetized needle could be deflected by an electric current, the needle could be made to move against a marked-off background and by the extent of the deflection, the amount of current could be measured. Ampère was attuned to this quantiza tion, for he was the first to try to apply advanced mathematics to electrical and magnetic phenomena. In 1823 he ad vanced a theory that the magnet’s prop erties arose from tiny electrical currents circling eternally within it. In this he was ahead of his time, for the existence of tiny electrically charged particles circling eternally was not to be known for three quarters of a century. Ampère’s contem poraries received his theories with great skepticism. In Ampère’s honor it is now conven tional to measure the quantity of electric current passing a given point in a given time in amperes, a usage originated by Kelvin [652] in 1883. This is justified since he was the first to differentiate the rate of passage of current from the driv ing force behind it. The latter is mea sured in volts in honor of Volta [337]. Ampère died of pneumonia, and his judgment of his own life is indicated by the sorrow-laden epitaph he chose for his own gravestone—‘Tandem felix” (Happy, at last). [408] MALUS, Étienne Louis (ma- lyoos') French physicist Born: Paris, July 23, 1775 Died: Paris, February 24, 1812 Malus was the son of a government official, so his youth was filled with a va riety of difficulties. Attending a military engineering school during the French Revolution, he was dismissed without a degree because his father had served the monarchy, which meant that he himself was suspected of undesirable political ac tivity. He switched to the newly founded École Polytechnique, where he was a classmate of Biot [404] and was involved with Biot in the street riot of 1795 that was put down by the young Napoleon. Malus was not as marked by anti Napoleonic feelings as Biot was, perhaps because, as a military engineer, he would naturally approve a successful general. He went on to serve in Egypt with Na poleon in 1798 and barely survived that disastrous campaign. Malus worked in optics as a hobby. The Paris Academy of Sciences had offered a prize for the best mathematical theory accounting for double refraction and Malus was interested in it. One day in 1808 he idly pointed his doubly re fracting crystal of Iceland spar at the sunlight reflected from a window and found that only one ray of light was emerging from the crystal. Through a mistaken theory that he had of the na ture of light, he believed the two re fracted rays ordinarily passing through the Iceland spar represented different
[409] KIDD
STROHMEYER [411] poles of the light (analogous to magnetic poles). He called the rays “polarized light,” therefore, a name it bears to this day. He concluded from his observation of the reflected sunlight that light could be polarized by reflection. He also concluded that the two re fracted rays emerging from the Iceland spar were polarized perpendicularly to each other, for it was possible to arrange matters so that as the crystal turned, one ray would fade out while the other strengthened, the two fading out com pletely but alternately with each ninety- degree turn of the crystal. All this was neatly explained by Fresnel’s [455] theory of transverse waves. In 1811 he was informed by Young [402] (despite the war that was at that time existing between Great Britain and France) that he had been awarded the Rumford medal. Malus died in his thirty-seventh year of tuberculosis. [409] KIDD, John British chemist and physician Born: London, September 10, 1775
Died: Oxford, September 17, 1851 In 1803 Kidd, the son of a ship’s cap tain, was appointed professor of chemis try at Oxford after having obtained his M.D. there two years before. His most important discovery came in 1819, when he obtained naphthalene from coal tar. Murdock [363] a quarter century earlier had pioneered the use of coal as a source of gaseous fuel, but Kidd pointed the way toward the use of coal as a source for chemicals. The sub stances in coal tar were important not only in themselves but, as Perkin [734] was to show a generation later, they were even more important as the starting material for synthetics that would put the naturally occurring compounds in the shade.
French mathematician Born: Paris, April 1, 1776 Died: Paris, June 27, 1831 Germain was the daughter of a well- to-do merchant and managed to find books in the library at home out of which to teach herself Latin, Greek, and mathematics. It was enormously difficult for a woman to receive any kind of edu cation, however, for the opinion was that women’s minds were too limited for edu cation. And by refusing them an educa tion and by hammering inferiority into them, their minds were made limited. Germain was forced to study the notes of other students who attended the École Polytechnique that she was not allowed to attend, then sent in a report under a male pseudonym. Lagrange [317] was as tonished at its worth, discovered the au thor was a woman and, to his credit, sponsored her thereafter. She did important work on Fermat’s [188] last theorem. Euler [275] had proved it for n = 3 and Legendre [358] for n = 5. Germain proved it for any prime under 100 where certain condi tions are met. She also worked out a mathematical model that explained the vibrations of a flat plate, such as that Chladni [370] used to work out his figures.
Germain even impressed the self-cen tered Gauss [415] with her worth. Gauss arranged to have her receive an honorary doctor’s degree from Gottingen, but Germain died before it could be awarded. We can only wonder how many mar velous feminine brains were stultified and prevented from fulfilling themselves and serving humanity because of the cruel and stupid male chauvinism that has permeated so much of society for so long a time. Download 17.33 Mb. Do'stlaringiz bilan baham: 
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