Monographs and books

Buffeted by conflicting ideologies, numerous intellectual movements, prolific authors, and cheap printing, the nineteenth century unleashed an unprecedented flood of the printed word. With the growth of education, professors took on a greater importance in publishing materials for the educational system and in writing works for the educated public. Among the most colossal scholarly works, although not the most perfect, were Migne's editions of the Patrologia latina in 221 volumes (1844–55) and the Patrologia graeca in 166 volumes (1857–66). The growth and popularization of science led to series like Reinwald's Bibliothèque des sciences contemporaines. The social sciences and philosophy had a famous outlet in the publisher Alcan's Bibliothèque contemporaine, many of whose volumes were written by his fellow normaliens. By 1904 Alcan's Bibliothèque scientifique internationale, under the editorship of Emile Alglave, included 103 volumes, many of which were adopted by the Ministry of Education for inclusion in the libraries of lycées and collèges, although only about fifty of the volumes (including translations) were in physics, chemistry, biology, and physiology. Much of Alcan's list was made up of excellent works in the haute vulgarisation of science; Alcan did not achieve the same distinction in scientific publication as it did in philosophy, history, and psychology.

The trouble with prizes

The history of the funding of science in France is pervaded by the theme of poverty, eloquently stated by a line of lamenters from Pasteur to Maurice Barrès and on to Jacques Monod. So convincing has been the brief for poverty that historians, ever victims of their sources, have generally been mesmerized into repeating this litany. Not that Pasteur was wrong in 1868: Dumas, Foucault, Fizeau, and Boussingault had private laboratories because there were no funds specifically earmarked for research in the educational budget. In 1884 Fremy echoed Dumas's plea of 1881 that those with money support science, but few followed Fremy's example of making a gift of 5,000 francs. Twenty-seven years later Georges Lemoine deplored the insufficiency of funds for the support of the scientific community, a vastly larger entity than it was in 1868, but seemingly in the same penury. Not really, of course; and it is to the steady, solid, increasing financial support for scientific research that the historian must also direct his attention. Recent scrutiny of the science support system in France has already produced some surprises, especially in the studies by Shinn, Crawford, and Weart.

The changing organization of French scientific research in the 1930s might easily be interpreted as a sign of confusion and vacillation, in tune with national politics. Nothing could be more mistaken. A strong sense of purpose animated the scientific community, whose devotion to the research imperative along with its persistent political lobbying had already produced by 1930 the foundations of state organization and funding of research. This basic fact is somewhat obscured by the birth of several different organizations with similar names during the 1930s; fortunately for the memory of posterity, they were all gobbled up by the Centre national de la recherche scientifique, the mega-organization created in 1939. Breton's Office des inventions, which had absorbed the Caisse des recherches scientifiques (1901–22), so adept at survival in the 1920s, was replaced in 1938 by the Centre national de la recherche scientifique appliquée, an ephemeral creature that expired in 1941. In 1930 parliament created two funds, one for letters and one for science. The Caisse nationale des sciences for the support of scientific research used a system of short, renewable contracts rather than create a permanent group of researchers. There was a novelty here. The state had set a new direction by granting research scholarships, for it now pushed the creation of a corps of researchers, rather than just pay for research materials.

In 1875, after nearly half a century of battle, French Catholics broke the tenacious monopoly of the state University in higher education. Although still hindered by onerous state regulations, the episcopacy founded five universities, strategically established in Paris, Lille, Angers, Lyon, and Toulouse. All served a certain group of dioceses. Except for Toulouse, they had at least the three faculties legally required for the establishment of a private university. The law also required that a faculty of science possess physics and chemistry laboratories as well as collections of instruments and material in physics and natural history. In spite of the jealous reassertion of some of the state University's old monopolistic prerogatives by the Ferry laws, involving, among other things, the elimination of professors of the Catholic faculties from examination juries and the denial of the title university to the new establishments, the Catholic institutions survived and still exist. Ferry was minister of education from February 4, 1879, to November 14, 1881, and from February 21 to November 20, 1883. Catholics interpreted the law of March 18, 1880, as a serious blow against the private faculties.

The dynamical interaction of material bodies does not consist in their gravitational attraction alone. Electric and magnetic forces between them have been known for a very long time and have by Faraday and Maxwell been reduced to the notion of the electromagnetic field. In ordinary circumstances electromagnetic forces are, whenever they are observed at all, very much stronger than the gravitational pull, which is exceedingly weak unless at least one of the interacting pieces of matter is very large, of the size of a celestial body. Of late, one has been induced to admit that between the elementary particles (nucleons) which go to build up the nucleus of an atom there is a force (called the nuclear force) which is perceptible only at very small distances, but outweighs there even the strong electric repulsion between some of those particles. The field of this force is usually referred to as the meson field, for reasons on which we will not enter at the moment.

Ever since Finstein discovered his theory of the gravitational field in 1915, there have been unceasing attempts to generalize it so as to account in the same natural way for the electromagnetic field as well. Since the latter is in empty space described by an antisymmetric tensor of the second rank, the idea suggests itself at once that one should take the fundamental tensor gik to be non-symmetric, hoping that its skew part ½(gik − gki) should have something to do with electromagnetism. But this plan meets with a certain difficulty. We had established Einstein's field equations in two steps.

In Einstein's theory of gravitation matter and its dynamical interaction are based on the notion of an intrinsic geometric structure of the space-time continuum. The ideal aspiration, the ultimate aim, of the theory is not more and not less than this: A four-dimensional continuum endowed with a certain intrinsic geometric structure, a structure that is subject to certain inherent purely geometrical laws, is to be an adequate model or picture of the ‘real world around us in space and time’ with all that it contains and including its total behaviour, the display of all events going on in it.

Indeed the conception Einstein put forward in 1915 embraced from the outset (and not only by the numerous subsequent attempts to generalize it) every kind of dynamical interaction, not just gravitation only. That the latter is usually in the foreground of our mind—that we usually call the theory of 1915 a theory of gravitation—is due to two facts. First, its early great successes, the new phenomena it predicted correctly, were deemed to refer essentially to gravitation, though that is, strictly speaking, true only for the precession of the perihelion of Mercury. The deflexion of light rays that pass near the sun is not a purely gravitational phenomenon, it is due to the fact that an electromagnetic field possesses energy and momentum, hence also mass. And also the displacement of spectral lines on the sun and on very dense stars (‘white dwarfs’) is obviously an interplay between electromagnetic phenomena and gravitation.

It is far beyond the scope of these lectures to report on the development of the ideas, first of Restricted, then of General, Relativity and to show how they are logically built on the outcome of a number of crucial experiments, as the aberration of the light of fixed stars, the Michelson-Morley experiment, certain facts regarding the light from visual binary stars, the Eötvös-experiments which ascertained to a marvellously high degree of accuracy the universal character of the gravitational acceleration—that is to say that in a given field it is the same for any test-body of whatever material.

Yet before going into details about the metrical (or Riemannian) continuum, I wish to point out the main trend of thought that suggests choosing such a one as a model of space-time in order to account for gravitation in a purely geometrical way. In this I shall not follow the historical evolution of thought as it actually took place, but rather what it might have been, had the idea of affine connexion already been familiar to the physicist at that time. Actually the general idea of it emerged gradually (in the work of H. Weyl, A. S. Eddington and Einstein) from the special sample of an affinity that springs from a metrical (Riemannian) connexion—emerged only after the latter had gained the widest publicity by the great success of Einstein's 1915 theory. Today, however, it seems simpler and more natural to put the affine connexion, now we are familiar with it, in the foreground, and to arrive at a metric by a very simple specialization thereof.