Euler wrote a number of works of great importance to the development of pure mathematics. The present book established analytical mathematics as an independent science and reduced analytical operations to a much simpler basis. Many of his principles are still used in teaching mathematics.

Rousseau (1712-78) was fundamentally at odds with the established beliefs of his time. In the Age of Reason he advocated the greater force of intuition: against artificial refinement, he urged a return to the natural state. So, defying the absolute monarchy of France, he published his exposition of the social contract, never more clearly or powerfully stated, that government is dependent upon the mandate of the people. It had a profound influence on French political thought, and was perhaps more directly the cause of the Revolution than any other single factor. This is probably the second of two printings in 1762. The first, from the Lilly collection, is also exhibited.

In this codification of the work of his predecessors, the further consequences of the theories of Newton, Euler, d'Alembert, and Lagrange were brilliantly expounded. Laplace developed an analytical theory of tides, deduced the mass of the moon, improved the calculation of cosmic orbits, and predicted that Saturn's rings would be found to rotate. Most notably of all, he propounded the modern Nebular Hypothesis, independently adumbrated by Kant.

De Graaf (1641-73) and Haller (1708-77) had investigated the processes of ovulation, but it was left for Baer to plot the course of fertilization from its later stages back to the ovary and there to identify the minute cell which was the ovum. In a second great work, Über Entwicklungsgeschichte der Tiere, 1828-34, he enlarged the field of investigation, and became the founder of modern embryology.

Brown observed under a microscope the irregular movement of minute particles in liquid now known as the "Brownian movement." This movement was explained by Ramsey in 1879 as being due to bombardment of molecules, which was experimentally proved by Perrin in 1908 who was also able to calculate the weight of the molecule of water. The principle involved was further developed by Einstein. This paper also made a contribution to the theory of colloids.

When Faraday was 41 he published the first- and when he was 64 the last- of his original scientific papers on electro-magnetism. They are the foundations of a large part of modern electrical engineering. Faraday himself said of them "it does surprise even my partiality, that [the different parts] should have the degree of consistency and apparent general accuracy which they seem to me to present," and, of the second, "I regret the presence of those papers which partake of a controversial character."

Schwann adopted the cell theory which Schleiden had propounded but misapplied in 1838. He expanded it into a general theory as the basis of all vital phenomena. He anticipated Pasteur's fermentation theories, and discovered and named pepsin.

Perhaps the most controversial of the Tracts for the Times ("On the Privileges of the Church and against Popery and Dissent") issued by the leaders of the Oxford Movement. The argument of this tract is to the effect that the XXXIX Articles are capable of being interpreted in a sense compatible with the theology of the Roman Catholic Church. This alarmed many of the leaders of the Church of England, and led all but two of the Heads of houses at Oxford to condemn it.

Chadwick's epoch-making reports as chief executive officer of the newly formed Poor Law Commission. Young, in Early Victorian England, says of the report that it is "a step from which descends by regular stages the Health Board of 1848, the Local Government Board of 1870, the existing Ministry of Health." Engels quotes extensively from this report in his book The Position of the Working Classes of England.

This and the companion volume on agriculture entitled him to be regarded as the founder of modern organic and inorganic chemistry. His analyses of innumerable compounds led to syntheses in the laboratory and, for example, to the great artificial fertilizer industry. He founded biochemistry by his researches into the raw materials of which organisms are built.

Boucher could not reconcile his discovery of flint implements at Abbeville with the accepted Mosaic cosmogony on Ussher's calculations. He was ridiculed by the orthodox, but his postulate of much more remote human antiquity is now accepted.

This work contains the first comprehensive statement of the law of the conservation of energy— all kinds of energy, heat, light, electricity, and all chemical phenomena, are capable of transformation from one to the other, but are indestructible. Tartaglia, Carnot, Mayer, and Joule made contributions to this theory, but Helmholtz proved it mathematically as capable of universal application. His work led to the construction of efficient heat engines and eventually to the liquefaction of all known gases. Helmholtz invented the ophthalmoscope in 1851 and made many important contributions to physiology, mathematics, and electricity.

Gobineau championed the theory that "race" is permanent and unchangeable, and proclaimed the Nordic or, as he called them, "Aryan" peoples to be the élite, destined to rule the rest of mankind. Although he considered the Germans a poor mixture of Celts and Slavs, his theories were adopted with special fervour in Germany because they seemed to provide a biological foundation for racism, anti-semitism, and pan-Germanism, culminating in national socialism.

On 30 November 1854 de Lesseps received a concession from the Egyptian Viceroy which authorized the construction of a canal across the Isthmus of Suez. The indifference of the Sultan and the declared opposition of the British were serious obstacles which de Lesseps had to overcome, with other obstacles nearer home. The first step was to outline his project in full in this book. Construction was begun in 1859, and the canal was formally opened to traffic ten years later.

Human remains handed by quarry workers in the Neander Valley to Fühlrot, an Elberfeld archaeologist, were described in these two papers presented jointly with Schaafhausen to a Rhineland natural history society. Described more fully and publicly in Müller's Archiv in 1858 they evoked Virchow's pronouncement that the skull was that of an idiot. Huxley took the discovery as a cornerstone in Man's Place in Nature, 1863, and thus the human race was brought within the scope of evolutionary theory.

Faraday discovered that electricity could influence a light beam. Maxwell's twenty equations proclaimed the electromagnetic nature of light which brought both electricity and light within the scope of dynamics, the wave theory of electricity which led to wireless, and the corpuscular theory of electricity which foreshadowed the electron. The further implications of this discovery were worked out by Einstein.

The first intelligible sentences exchanged over the telephone, were from one room to another in the same house. They were "Do you understand what I say?" "Yes; I understand you perfectly." In the same month, March 1876, Bell took out his first patent which, though often contested, was uniformly upheld by the courts. Bell was born in Edinburgh. He became an American citizen in 1874.

In this short paper Koch announced his isolation of the tubercle bacillus, and the special culture and differential staining methods he had first introduced in 1876. These new methods of identifying and later of photographing microscopic objects were further advanced by Ehrlich. Koch's great work on the etiology of surgical infections, 1878, is a medical classic.

The culmination of his aristocratic nihilism, his revolt against all convention, religious or social, cast in aphoristic form with epigrammatic wit and force of expression, are best displayed in this psuedo-prophetical work.

In 1878 Booth founded the Salvation Army, and in 1890, the same year that Stanley published In Darkest Africa, he published In Darkest England and The Way Out. In this book he analyzed the causes of the pauperism and vi ce of the period, and proposed a remedy by ten expedients. These included land settlement, emigration, rescue work among prostitutes and at the prison-gate, the poor man's bank, and the poor man's lawyer. Money was liberally subscribed, and a large part of the scheme was carried through.

Though the use of fingerprints as identification marks is of very ancient origin, Galton was the first to explain their possibilities for identifying criminals. He also wrote Decipherment of Blurred Finger Prints (1893) and Finger Print Directories (1895). These investigations formed part of the general scheme of "Eugenics" formulated by Galton.

Investigating Clerk Maxwell's conception of light as an electromagnetic phenomenon, Hertz discovered that waves of electricity could be transmitted and received through space. This led directly to Marconi's perfection of wireless telegraphy.

Concerned to extend the electromagnetic theories of Maxwell, Lorentz made the fundamentally new assumption that the behaviour of light and matter was explicable on the assumption of atoms of electricity, now called electrons. Later his hypothesis that a moving object is shortened in the direction of its movement was adopted by Einstein.

The discovery of X rays—"a new type of radiation"—by the fifty-five-year-old Röntgen, professor of physics at Würzburg, in 1895, marks the real starting-point of modern physical research. Such was the impact of this discovery on the world of science that in the next twelve months more than a hundred papers treating of these new effects appeared in the journals, over the names of scientists both amateur and professional, Becquerel was directed to the discovery of radioactivity by Röntgen's discovery; and X-ray analysis in the hands of such as Aston, Moseley, the Braggs, and Perutz and his colleagues has revolutionized modern science.

Whatever may be claimed for other early experimenters in cinematography, it is certain that Lumiére was the first to produce a practical machine with commercial possibilities. This brochure was his first public announcement of his invention, and several of the films listed in it were shown at the memorial exhibition in Paris in 1937 and found to be as good as new. It is worth noting that the reason for complete lack of flicker in these early films was the fact that Lumière used the same machine for both taking and projecting his films.

Distressed by the overcrowding in large cities Howard wrote this impassioned plea for taking the city into the country-side. In 1903 he persuaded a group of financiers that this was a business proposition, and the first garden city in the world was begun at Letchworth. He was a poor man all his life but was knighted in 1927.

World-famous experiments on dogs by which salivary reactions were produced by a kind of Barmecide feast, first "psychical secretions" and later "conditioned reflexes." The first full statement of Pavlov's experiments in English was in Conditioned Reflexes, 1927.

Ernest Jones, Freud's biographer and friend, wrote of this book: "It is without any doubt Freud's greatest work, and one which contains the germ of all his later work." Its conclusions were completely new and totally unexpected. It contains all the basic features of psychoanalytic theory and practice—the erotic nature of dreams, the "Oedipus complex," and, above all, the theory of the unconscious and the libido. The new field of study opened by this one man is still largely unexplored and its implications have revolutionized our thinking in many fields.

The point of departure from the Social-Democrats, or Mensheviks, is here laid down. Denunciation of "spontaneity," "opportunism," and "democracy" are explicit. The need for a monolithic party ready to assume dictatorial powers—the complete basis of the seizure of power in 1917 is contained in What is to be done? Stuttgart publication is explained by its being the headquarters of Lenin and his fellow political exiles at the time.

Inspired by Poincaré's exhibition in 1896 of radiographs sent him by Rö ntgen, Becquerel deliberately sought to investigate other phosphorescent phenomena. Accidental fogging of photographic plates in his dark room was traced to the presences of uranium ore, and this led to the theory of radioactivity. He suggested to the Curies that pitchblende might repay investigation and thus set them on the trail that led to radium.

Becquerel, following the discovery of Röntgen, had discovered the fact of radioactivity in 1896. Madame Curie read a paper on the subject to the Académie des Sciences, and in 1903, in two modestly entitled theses, she announced the final laborious isolation of radium.

Two indispensable features for the extension of Einstein's special theory of 1905 into a universal theory in 1916 were here expounded: (a) time as a fourth dimension, one second corresponding to the distance travelled by light in that time, and (b) the corollary of a space-time continuum. In this new space conception, Euclidean geometry would not work, and thus the pioneering of Lobatchewsky and Riemann was perfected.

This collaboration between a German chemist and a Japanese bacteriologist resulted in the discovery of Salvarsan ("606"), a specific cure for syphilis. This led to their theory of chemotherapy, the discovery of a specific that would kill bacteria without harming the host, and to modern antibiotics. Ehrlich also advanced considerably methods of differential staining in microscopy.

F.W. Taylor, an American engineer employed by the Bethlehem Steel Company, was the founder of "scientific management" in industry. He laid down the main lines of approach to the problem of increased efficiency by standardizing processes and machines, time and motion study, and systematizing "piece-work" or payment by results. All these systems have been welcomed in Russia, but are anathema to trades-unionists almost everywhere else.

Laue had suggested that the regular arrangement of atoms in a crystal would provide a diffraction grating sufficiently fine to produce spectroscopic effects from X rays and thus prove that these are light waves of very short wavelength. The Braggs tackled the problem from the other end, concentrating on the knowledge of atomic structure which X-ray shadows could provide. This has revolutionized both pure and applied chemistry. The discoveries of Aston and Moseley were immediate sequels in pure science. The discovery of the chemical basis of life—DNA—by Perutz and others is only the most recent of the sensational results of the Braggs experiments.

Moseley used the crystal method of analysis for determining the wavelength of X rays to the spectra of the elements. From his results he deduced that a new atomic number could be attached to each element based on its nuclear charge. This replaced the fallible table based on atomic weights—a discovery as fundamentally important as the discoveries of the periodic table itself and of spectrum analysis. Four new elements were immediately discovered by his method.

Einstein was on the track of his theory of gravitation ("general relativity theory") in 1913-14. In this paper the theory first appears fully fledged. Its importance was at once recognized by specialists, but it was not until 1919, when one of its leading predictions was confirmed by the British Eclipse Expeditions, that it attained public notoriety. It has been said that in 1919 not more than a dozen people in the world had mastered the theory, and not one of them could understand any of the popular summaries of it. The copy shown belonged to Eddington and has his notes.

Rutherford revolutionized the science of radioactivity in countless ways. Photographs of the tracks of alpha particles which Rutherford shot through nitrogen showed hydrogen atoms emerging from the nuclei of the bombarded element. He described this as "controlled distintegration of the elements." We know it as nuclear fission with its end-product, the H-bomb.

Aston, a pupil of Thomson, developed one of the first efficient spectroscopes which enabled him to discover many isotopes as the constituents of chemical elements. He discovered 212 of the 281 naturally occurring isotopes, and was able to measure with great precision their exact masses which are fundamental to the nuclear theory and the development of nuclear energy—leading directly to Urey's discovery of "heavy water."

The programme of a political gangster who herein told the timid and incredulous politicians of his own and other nations exactly and in detail what he would do if he had the power.

In 1865 Clerk Maxwell correlated electricity and light. Einstein's repeated attempts to bring gravitation within the same correlation were successfully completed in this paper. Thus every form of activity within the sphere of physics was united in a common explanation, and the theory of relativity was perfected. The first of a series of papers on this subject.

This report concludes: "With respect to the abstract question of mechanical flight we are still ignorant of the rudimentary principles (but) no tangible evidence has been brought forward to show that mechanical flight is an impossibility for man."

A foundation-stone of modern aeronautics, the most detailed and accurate series of observations ever made on the properties of curved wing surfaces. Based on these Lilienthal built his first glider in 1891 and began the sensational feats of gliding which ultimately cost him his life.

Langley, with only a high school education, was a pioneer in solar radiation and became third Secretary of the Smithsonian Institution. Becoming interested in aviation he devised novel instruments for lift and drift of the moving plane surfaces, described here. These resulted, in 1896, in the first sustained free flights of power-propelled heavier-than-air machines ever made.