Biographical encyclopedia
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266 [397] HUMBOLDT
SEEBECK [398] one passed from the poles toward the equator and, also, the rate of tempera ture drop with altitude. He observed a rich meteor shower and his report helped increase scientific interest in the phenom enon, paving the way for Chladni [370] and Biot [404]. He also reported on In dian antiquities, and introduced Europe to the fertilizing powers of the Peruvian guano. He was the first to see the practi cality of a canal through Panama— something that would not become an ac tuality until the work of Gorgas [853] a century later. In Ecuador he even climbed the volcano Chimborazo, which is nineteen thousand feet high, and that set a record that no one was to better for a generation afterward. He stopped off in the new nation of the United States on his way back to Europe, visiting President Thomas Jeffer son [333]. Back in Paris, Humboldt wrote of his travels to America in most engaging fashion (he was an excellent writer and had artistic talents as well) and founded an international society for the study of terrestrial magnetism. He conducted ex periments on the composition of the at mosphere with Gay-Lussac [420]. By some, he was considered the most spec tacular man in Europe next to Napoleon himself. (Humboldt and Napoleon were born only a month apart, but Napoleon lived only half as long and came to a bad end.) After the fall of Napoleon, Humboldt served the Prussian king, Frederick Wil liam III, as a diplomat and, eventually, his money running out at last, he ac cepted a salaried post in Berlin, in which he was the titular head of the Prussian school system. He retained the privilege of frequent visits to Paris, where he was happiest, and where he could serve Prus sia as liaison man with King Louis Phi lippe of France (a personal friend of his). Throughout his life, he retained a lib eral, democratic attitude, quite at vari ance with the growing conservatism in Prussia. He applauded the French Revo lution, inveighed against human slav ery in the Americas and was an influence for the better on young Simon Bolivar who eventually led Latin America in its struggle for freedom from Spain. Hum boldt’s purse, like that of Banks [331], a generation before, was always at the ser vice of poor but promising scientists. His restless mind kept him busy. He suggested the use of isothermal lines (lines marking equal temperature levels) on the world map as one method of un derstanding the geography of our planet and the life upon it. In 1829 he was invited by the Russian tsar Nicholas I to explore the vast Asian dominions over which he ruled, and this Humboldt did in a kind of whirlwind trek.
Finally, in his seventies Humboldt began to organize the gathered knowl edge of his life into a book called
implied, to give a truly cosmic view of the earth; to see it whole, all in one piece. Certainly, no man before him, with so active a mind, had seen so much of the world, and no man before him was so well equipped to write such a book. Fortunately he lived long enough to complete it despite his late start, though the fifth and last volume did not appear until after his death. It was a florid production, rather overblown, but it is one of the remark able books in scientific history and was the first reasonably accurate encyclo pedia of geography and geology. In this book Humboldt might almost be said to have founded the science of geophysics. When he died, in his ninetieth year, he was given a state funeral, and all of scholarly Europe mourned. [398] SEEBECK, Thomas Johann (zay'- bek) Russian-German physicist Born: Revel, Estonia (now Tal linn, Estonian SSR), April 9, 1770 Died: Berlin, Germany, Decem ber 10, 1831 Seebeck, born of a well-to-do mer chant of German descent, studied medi cine at the universities of Berlin and Gottingen, receiving his M.D. from the latter institution in 1802. He was a
[399] TREVITHICK BICHAT
friend of Goethe [349] and worked with him on his wrongheaded theories about color.
More fruitfully, in the long run, See beck was the first to observe, in 1821, that if two different metals were joined at two places, and the two points of junction were kept at different tempera tures, an electric current would flow con tinuously round the circuit. This conversion of heat into electricity (“thermoelectricity”) was not properly interpreted by Seebeck himself and it was not followed up. The “Seebeck effect” lay in abeyance for over a cen tury, therefore, though it is now fruit fully used, particularly in connection with the semiconductor devices first pro duced by Shockley [1348] and his co workers. [399] TREVITHICK, Richard (treh'vih- thik) English inventor Born: Dlogan, Cornwall, April 13, 1771
Died: Dartford, Kent, April 22, 1833
Trevithick had a father who was pro fessionally involved in coal mining. The young man grew interested in steam en gines early (his father was one of the first to install the Watt [316] engines) and developed a model that made use of higher pressures than those of Watt. This was a retreat to Savery [236] a century and a quarter before, in a sense. How ever, metallurgical techniques were im proving and machinery was now ade quate to handle high-pressure steam. In 1796 Trevithick was designing steam locomotives and in 1801 an engine of his pulled passenger trains. It was Trevithick who proved that smooth metal wheels on smooth metal rails would supply sufficient traction to pull trains. Trevithick, encouraged by men such as Rumford [360] and Davy [421], had many novel and ingenious ideas— too many, for he tried to act on them all. He did not concentrate sufficiently on any one of them and he could make no one of them succeed thoroughly, not even his locomodves. Then, too, like Fitch [330], Trevithick was plagued by incredibly bad luck. His locomotives worked but he had to face broken axles, insufficient steam, fire, public hostility. In the end, he had to see credit go to a later and more fortunate man. Where Fitch had his Fulton [385], Trevithick had his Stephenson [431], In South America, where he had gone to introduce his steam engines, he built pumps for the silver mines of Peru but was stranded as a result of the revolt of the Spanish colonies. He was forced to take part in the fighting; and he returned to England only by borrowing money from Stephenson’s son, who happened to be in South America at the time and whose money came from the dividends of a successful railroad. Trevithick continued to the end of his life to have more ideas than he could handle, and he died in poverty, having been unable to persuade Parliament to vote him a grant in return for his inven tive achievements. He had a pauper’s burial and an unmarked grave. [400] BICHAT, Marie François Xavier (bee-shahO French physician
14, 1771 Died: Lyon, July 22, 1802 Bichat was the precocious son of a physician and eagerly entered a medical career. He began work in Lyon but the tumult of the French Revolution (he was a moderate republican) drove him out of that city and into Paris in 1793 (though Paris was entering the Terror at the time). Like Morgagni [251] nearly a century earlier, Bichat’s advances arose out of the numerous postmortems he conducted. There were as many as six hundred of these in the final year of his short life, during which he never mar ried. He was the classical biological ob server, with the eye (unaided even by a microscope, which he distrusted) as his chief tool. Nor did he seek to probe deeper, for he was an extreme vitalist who denied that physics or chemistry 268 [401] MOHS
YOUNG [402] could possibly aid in the understanding of life. He was the first to draw the attention of the anatomist and the physiologist to the organs of the body as a complex of simpler structures, but he gave due credit to Pinel [338] who had moved in this di rection. Though working without benefit of microscope he was able to show that each organ was built up of different types of “tissues” (a term he himself in troduced, using it because they were gen erally flat and delicately thin layers). Furthermore, different organs might pos sess some tissues in common. All told, he identified twenty-one types of tissues, published his book on the subject, Gen eral Anatomy, in 1800, and may be con sidered the founder of histology. This was an important step in the di rection of the cell theory of life, which was to come with the work of Schleiden [538] and Schwann [563] a generation later. Bichat might well have lived to see this ordinarily, but he died at the age of thirty, shortly after fainting and falling down the stairs in his laboratory. Had he lived longer, it might not have been so easy to decide that Laënnec [429] was the most distinguished French physician of the early nineteenth century. [401] MOHS, Friedrich (mose) German mineralogist Born: Gemrode, Anhalt-Bem- burg, January 29, 1773 Died: Agardo, Italy, September 29, 1839 Mohs, a student of Werner [355], taught in Austria and Germany and is best known today for the fact that he devised the Mohs scale in 1822. This is a standard by which the hardness of min erals can be expressed. To make use of the scale, the smooth surface of the mineral to be tested is scratched by the sharp edge of a series of substances of graded hardness. A sub stance can be scratched by one harder than itself and can in turn scratch one softer than itself. The scale ranges from 1 for the soft mineral, talc, to 10 for dia mond. The numbers do not, in actual fact, measure equal differences in hard ness. He died on a journey to southern Italy, where he planned to study the vol canic areas. [402] YOUNG, Thomas English physicist and physician Born: Milverton, Somerset, June 13, 1773 Died: London, May 10, 1829 Young, the son of a Quaker banker, was an infant prodigy who could read at two and who had worked his way twice through the Bible at six. During his youth, he learned a dozen languages in cluding not only Greek, Latin, and He brew, but also Arabic, Persian, Turkish, and Ethiopian. He could also play a va riety of musical instruments, including the bagpipes. He was the best kind of in fant prodigy, the kind that matures into an adult prodigy. He was called Phe nomenon Young at Cambridge and there became financially independent on the death of a rich uncle in 1797. Young took up medicine and studied at the University of Edinburgh under the aged Black [298]. He went to Germany and obtained his degree at the University of Gottingen in 1796, then opened his practice in London in 1799. Between 1801 and 1803 he lectured on science at the Royal Institution, newly founded by Rumford [360], and in 1802 he was ap pointed foreign secretary of the Royal Society. As a physician he was unsuccessful be cause he lacked a suave bedside manner. He was interested in sense perception. He was the first to discover (while still a medical student) the manner in which the lens of the eye changes shape (ac commodation) in focusing on objects at differing distances. In 1801 he described the reason for astigmatism: the fuzziness of vision arose from the irregularities of the curvature of the cornea. It was an easy step from the eye to light itself. For more than a century now there had been a controversy as to whether light consisted of particles or of waves, particle supporters having much the best of it. The most important evi 269 [402] YOUNG
YOUNG [402] dence against waves was the fact that light cast sharp shadows and did not make its way around comers as sound waves did. Some had suggested that the smaller the size of waves, the less bend ing they did and that the wavelengths of light might be so small that the bending was exceedingly minute. Grimaldi [199] had, in actual fact, detected this minute bending a century and a half before, but his observations had been neglected. It fell to Young to demonstrate the wave nature of light in more dramatic fashion. Young accomplished this in 1803 by sending light through very narrow open ings and showing that separate bands of light appeared where there should have been nothing but the sharply shadowed boundary of the edge of the opening. These bands of light arose from the kind of diffraction around corners that Gri maldi had noted, and it could not be ex plained by the particle theory. Young had a more conclusive piece of evidence. From his study of sound he grew interested in the phenomenon of beats, in which two different pitches of sound produced periods of intensified sound separated by periods of silence. This was easily explained, since the two pitches had different wavelengths and therefore did not keep step. At first the two waves might be temporarily in step and the two wave peaks would reinforce each other to produce doubled sound. They would then fall out of step and the molecules of air would be pushed in one direction by one wave and in the oppo site direction by the other, with a net effect of motionlessness and—no sound. Now, then, would two light waves add up to produce darkness? If they were particles, they couldn’t; if they were waves, they could. Young introduced light beams through two narrow orifices. They spread out and overlapped. The overlapping region was not a simple area of intensified light but formed a striped pattern of alternating light and darkness, a situation (interference) exactly analo gous to beats in sound. At first Young’s work met with consid erable hostility in England, particularly as the result of the enmity of a personal antagonist, Henry Brougham, a baronet and an influential literary reviewer. Young’s mathematics was, besides, diffi cult and his exposition rather fuzzy. For another thing, the particle theory was particularly “English” since it had been introduced by Newton [231] and there were psychological difficulties concerning its rejection by English physicists though Wollaston [388] supported him vigor ously. (National pride often plays a role in science—almost always a deleterious one.) It therefore fell to Frenchmen, Fresnel [455] and Arago [446], to do the necessary follow-up work that was to es tablish Young’s work and to strike down the particle theory (if not forever, then at least for nearly a century). From his diffraction experiment, Young was able to calculate the wave length of visible light, for it was only necessary to figure out what wavelength would allow the observed degree of small bending. The wavelengths turned out to be very small indeed, being less than a millionth of a meter. Young’s interest in light also led him to consider the manner of color percep tion. He was the first to suggest that it was not necessary to see each color sepa rately by some different physiologic mechanism. It was enough to see three colors: say red, green, and blue. Combi nations of these in various proportions would give the effect of all the myriads of shades of different colors. This theory was further refined by Helmholtz [631] a half century later and is usually referred to as the Young-Helmholtz three-color theory. The color photography and color television of the twentieth century make use of this three-color theory. There remained an important question concerning light, even if the existence of waves were allowed. What type of waves would light waves be? They might be transverse waves, like the waves on a water surface, undulating at right angles to the direction of movement of the wave train as a whole. Or they might be longitudinal, like sound waves, undulat ing in the same direction as the move ment of the wave train. All the early proponents of the wave theory of light, notably Huygens [215], had taken longi tudinal waves almost for granted and so
[403] BROWN
BROWN [403] did Young at first. However, longitudinal waves could not explain the double re fraction first noted by Bartholin [210]. In 1817 Young wrote to Arago that the light waves must be transverse and that this would explain double refraction. In this he was correct. Young was interested in forms of en ergy other than light. In 1807 he was the first to use the word energy in its mod em sense—as the property of a system that makes it capable of doing work and as proportional to the product of the mass of a body and the square of its ve locity. In that year also he argued against the caloric theory of heat, citing Rumford’s experiments. Here, however, it was the French physicists who found it difficult to abandon the “French” theory of Lavoisier [334] and a half century passed before the caloric idea was de molished by Maxwell [692], an English man.
Young also contributed to an under standing of surface tension of liquids and reported on the nature of elastic substances. A constant, used in equa tions defining the behavior of elastic sub stances, is still called Young’s modulus. And as though this varied activity were not enough, Young contributed many and varied articles to the En cyclopaedia Britannica. He also reached beyond the physical and biological sci ences altogether and in 1814 took up the problem of the Rosetta Stone. This had been discovered while Napoleon was in Egypt, and was the key to the ancient hieroglyphic language of the Egyptians. He gave up his medical practice to do so and was the first to make progress in deciphering it. In 1818 this physician and physicist was able to write an authoritative article on Egypt that outshone the efforts of contemporaries who were merely histo rians, thus laying the groundwork for the definitive work to be done later by Champollion. [403] BROWN, Robert Scottish botanist Born: Montrose, Angus, Decem ber 21, 1773 Died: London, June 10, 1858 Brown was the son of an Anglican priest and studied medicine at the Uni versity of Edinburgh. He did not take a degree, however. As a young man he served in the army and spent his spare time (he was a medical officer and there fore had spare time) collecting plants. While stationed in Ireland, where he had been sent in 1795, he met Banks [331], (in 1798), who promptly took Brown under his wing. In 1801, through Banks’s influence, Brown obtained the post of naturalist on a voyage to the still-new and largely un known continent of Australia, dupli cating the feat of his sponsor, Banks, a generation earlier. The ship returned in 1805 with some four thousand species of plants.
In classifying the new plants, Brown made use of the microscope and, for the first time in England, made use of the natural system of Jussieu [345] and Can dolle [418] and not the artificial one of Linnaeus [276]. This completed the vic tory of the natural system. Brown was the first to separate the higher plants into gymnosperms and angiosperms. He worked on a huge treatise on his Australian plants, but only the first vol ume ever appeared. That was in 1810, and the next year he was elected to the Royal Society. As a consequence of his work Brown was also appointed librarian of the Lin- naean Society in 1810. He also served as librarian to Banks and when Banks died in 1820, his will left Brown in charge of his house, his library, and his collection of plants. Brown transferred the whole to the British Museum in 1827 but re mained in charge of it. Brown is remembered particularly for two discoveries. In his botanical re searches he, like others before him, was aware of a small body within the cells that composed the plant tissues. Brown, unlike his predecessors, recognized this as a regular feature of cells and in 1831 gave it the name by which it has been known ever since: “nucleus,” from the Latin word meaning “little nut.” The second discovery had startling re percussions quite outside the field of the life sciences, a development that Brown Download 17.33 Mb. Do'stlaringiz bilan baham: 
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