The 100 Most Influential Scientists of All Time (21 page)

By 1839 Faraday was able to bring forth a new and general theory of electrical action. Electricity, whatever it was, caused tensions to be created in matter. When these tensions were rapidly relieved (i.e., when bodies could not take much strain before “snapping” back), then what occurred was a rapid repetition of a cyclical buildup, breakdown, and buildup of tension that, like a wave, was passed along the substance. Such substances were called conductors. In electrochemical processes the rate of buildup and breakdown of the strain was proportional to the chemical affinities of the substances involved, but
again the current was not a material flow but a wave pattern of tensions and their relief. Insulators were simply materials whose particles could take an extraordinary amount of strain before they snapped. Electrostatic charge in an isolated insulator was simply a measure of this accumulated strain. Thus, all electrical action was the result of forced strains in bodies.

Since the very beginning of his scientific work, Faraday had believed in what he called the unity of the forces of nature. By this he meant that all the forces of nature were but manifestations of a single universal force and ought, therefore, to be convertible into one another. In 1846 he made public some of his speculations in a lecture titled “Thoughts on Ray Vibrations.” Specifically referring to point atoms and their infinite fields of force, he suggested that the lines of electric and magnetic force associated with these atoms might, in fact, serve as the medium by which light waves were propagated.

In 1845 Faraday tackled the problem of his hypothetical electrotonic state. He passed a beam of plane-polarized light through the optical glass of high refractive index and then turned on an electromagnet so that its lines of force ran parallel to the light ray. The plane of polarization was rotated, indicating a strain in the molecules of the glass. But Faraday again noted an unexpected result. When he changed the direction of the ray of light, the rotation remained in the same direction, a fact that Faraday correctly interpreted as meaning that the strain was not in the molecules of the glass but in the magnetic lines of force. The direction of rotation of the plane of polarization depended solely upon the polarity of the lines of force; the glass served merely to detect the effect.

By 1850 Faraday had evolved a radically new view of space and force. Space was not “nothing,” the mere location of bodies and forces, but a medium capable of supporting the strains of electric and magnetic forces. The energies of the world were not localized in the particles from which these forces arose but rather were to be found in the space surrounding them. Thus was born field theory. As Maxwell later freely admitted, the basic ideas for his mathematical theory of electrical and magnetic fields came from Faraday; his contribution was to mathematize those ideas in the form of his classical field equations.

(b. Nov. 14, 1797, Kinnordy, Forfarshire, Scot.—d. Feb. 22, 1875, London, Eng.)

S
cottish geologist Sir Charles Lyell was largely responsible for the general acceptance of the view that all features of the Earth's surface are produced by physical, chemical, and biological processes through long periods of geological time. The concept was called uniformitarianism (initially set forth by James Hutton). Lyell's achievements laid the foundations for evolutionary biology as well as for an understanding of the Earth's development. He was knighted in 1848 and made a baronet in 1864.

In the 1820s Lyell was rapidly developing new principles of reasoning in geology and began to plan a book which would stress that there are natural (as opposed to supernatural) explanations for all geologic phenomena, that the ordinary natural processes of today and their products do not differ in kind or magnitude from those of the past, and that the Earth must therefore be very ancient because these
everyday processes work so slowly. With the ambitious young geologist Roderick Murchison, he explored districts in France and Italy where proof of his principles could be sought. From northern Italy Lyell went south alone to Sicily. Poor roads and accommodations made travel difficult, but in the region around Mt. Etna he found striking confirmation of his belief in the adequacy of natural causes to explain the features of the Earth and in the great antiquity even of such a recent feature as Etna itself.

The results of this trip, which lasted from May 1828 until February 1829, far exceeded Lyell's expectations. Returning to London, he set to work immediately on his book,
Principles of Geology
, the first volume of which was published in July 1830. Lyell finished the second volume of
Principles of Geology
in December 1831 and the third and final volume in April 1833. His steady work was relieved by occasional social or scientific gatherings and a trip to a volcanic district in Germany.

In 1838 Lyell's
Elements of Geology
was published, which described European rocks and fossils from the most recent, Lyell's specialty, to the oldest then known. Like
Principles of Geology
, this well-illustrated work was periodically enlarged and updated.

In 1841 Lyell accepted an invitation to lecture and travel for a year in North America, returning again for nine months in 1845–46 and for two short visits in the 1850s. During these travels, Lyell visited nearly every part of the United States east of the Mississippi River and much of eastern Canada, seeing almost all of the important geological “monuments” along the way, including Niagara Falls. Lyell was amazed at the comparative ease of travel, and he often praised the speed and comfort of the new
railroads and steamships. Lyell wrote enthusiastic and informative books, in 1845 and 1849, about each of his two long visits to the New World.

In the 1840s Lyell became more widely known outside the scientific community. He studied the prevention of mine disasters with the English physicist Michael Faraday in 1844, served as a commissioner for the Great Exhibition in 1851–52, and in the same year helped to begin educational reform at Oxford University—he had long objected to church domination of British colleges. In the winter of 1854 he travelled to Madeira to study the origin of the island itself and its curious fauna and flora. After exhaustive restudy carried out on muleback in 1858, he proved conclusively that Mt. Etna had been built up by repeated small eruptions rather than by a cataclysmic upheaval as some geologists still insisted.

In 1859 publication of Darwin's
Origin of Species
gave new impetus to Lyell's work. Although Darwin drew heavily on Lyell's
Principles of Geology
both for style and content, Lyell had never shared Darwin's belief in evolution. But reading the
Origin of Species
triggered studies that culminated in publication of
The Geological Evidence of the Antiquity of Man
in 1863, in which Lyell tentatively accepted evolution by natural selection. Only during completion of a major revision of the
Principles of Geology
in 1865 did he fully adopt Darwin's conclusions, however, adding powerful arguments of his own that won new adherents to Darwin's theory.

(b. May 28, 1807, Motier, Switz.—d. Dec. 14, 1873, Cambridge, Mass., U.S.)

S
wiss-born U.S. naturalist, geologist, and teacher Louis Agassiz made revolutionary contributions to the study
of natural science with landmark work on glacier activity and extinct fishes. He achieved lasting fame through his innovative teaching methods, which altered the character of natural science education in the United States.

Agassiz's interest in ichthyology began with his study of an extensive collection of Brazilian fishes, mostly from the Amazon River, which had been collected in 1819 and 1820 by two eminent naturalists at Munich. The classification of these species was begun by one of the collectors in 1826, and when he died the collection was turned over to Agassiz. The work was completed and published in 1829 as
Selecta Genera et Species Piscium
. The study of fish forms became henceforth the prominent feature of his research. In 1830 he issued a prospectus of a
History of the Fresh Water Fishes of Central Europe
, printed in parts from 1839 to 1842.

The year 1832 proved the most significant in Agassiz's early career because it took him first to Paris, then the centre of scientific research, and later to Neuchâtel, Switz., where he spent many years of fruitful effort. Already Agassiz had become interested in the rich stores of the extinct fishes of Europe, especially those of Glarus in Switzerland and of Monte Bolca near Verona, of which, at that time, only a few had been critically studied. As early as 1829 Agassiz planned a comprehensive and critical study of these fossils and spent much time gathering material wherever possible. His epoch-making work,
Recherches sur les poissons fossiles
, appeared in parts from 1833 to 1843. In it, the number of named fossil fishes was raised to more than 1,700. The great importance of this fundamental work rests on the impetus it gave to the study of extinct life itself. Turning his attention to other extinct animals found with the fishes, Agassiz published in 1838–42 two volumes
on the fossil echinoderms of Switzerland, and later (1841–42) his
Études critiques sur les mollusques fossiles
.

From 1832 to 1846 Agassiz worked on his
Nomenclator Zoologicus
, a catalog with references of all the names applied to genera of animals from the beginning of scientific nomenclature, a date since fixed at Jan. 1, 1758. However, in 1836 Agassiz began a new line of studies: the movements and effects of the glaciers of Switzerland. In 1840 he published his
Études sur les glaciers
, in some respects his most important work. In it, Agassiz showed that at a geologically recent period Switzerland had been covered by one vast ice sheet. His final conclusion was that “great sheets of ice, resembling those now existing in Greenland, once covered all the countries in which unstratified gravel (boulder drift) is found.”

In 1846 Agassiz visited the United States for the general purpose of studying natural history and geology there but more specifically to give a course of lectures at the Lowell Institute in Boston. In 1847 he accepted a professorship of zoology at Harvard University. In the United States his chief volumes of scientific research were the following:
Lake Superior
(1850);
Contributions to the Natural History of the United States
(1857–62), in four quarto volumes, the most notable being on the embryology of turtles; and the
Essay on Classification
(1859), a brilliant publication, which, however, failed to grasp the fact that zoology was moving away from the doctrine of special creation toward the doctrine of evolution.

Besides these extensive contributions there appeared a multitude of short papers on natural history and especially on the fishes of the U.S. His two expeditions of most importance were, first, to Brazil in 1865 and, second, to California in 1871, the former trip involving both shores of
South America.
A Journey in Brazil
(1868), written by Mrs. Agassiz and himself, gives an account of their experiences. His most important paper on U.S. fishes dealt with the group of viviparous surf fishes of California.

Agassiz's method as teacher was to give contact with nature rather than information. He discouraged the use of books except in detailed research. The result of his instruction at Harvard was a complete revolution in the study of natural history in the U.S. The purpose of study was not to acquire a category of facts from others but to be able, through active contact with the natural world, to gather the needed facts. As a result of his activities, every notable teacher of natural history in the U.S. for the second half of the 19th century was a pupil either of Agassiz or of one of his students.

In the interests of better teaching and scientific enthusiasm, he organized in the summer of 1873 the Anderson School of Natural History at Penikese, an island in Buzzards Bay. This school, which had the greatest influence on science teaching in America, was run solely by Agassiz. After his death it vanished.

(b. Feb. 12, 1809, Shrewsbury, Shropshire, Eng.—d. April 19, 1882, Downe, Kent)

E
nglish naturalist Charles Darwin developed the theory of evolution by natural selection, which became the foundation of modern evolutionary studies. An affable country gentleman, Darwin at first shocked religious Victorian society by suggesting that animals and humans shared a common ancestry. However, his nonreligious biology appealed to the rising class of professional scientists, and by the time of his death evolutionary imagery had spread through all of science, literature, and politics.
Darwin, himself an agnostic, was accorded the ultimate British accolade of burial in Westminster Abbey, London.

Darwin formulated his bold theory in private in 1837–39, after returning from a voyage around the world aboard HMS
Beagle
, but it was not until two decades later that he finally gave it full public expression in
On the Origin of Species
(1859), a book that has deeply influenced modern Western society and thought.

Darwin embarked on the
Beagle
voyage on Dec. 27, 1831. The circumnavigation of the globe would be the making of Darwin. Five years of physical hardship and mental rigour, imprisoned within a ship's walls, offset by wide-open opportunities in the Brazilian jungles and the Andes Mountains, were to give Darwin a new seriousness. As a gentleman naturalist, he could leave the ship for extended periods, pursuing his own interests. As a result, he spent only 18 months of the voyage aboard the ship. Among the places Darwin visited on the voyage were the Cape Verde Islands, coastal regions of Brazil, Uruguay, and Argentina, and the Galapagos Islands.