Born in Paris in 1743, Antoine Laurent
belonged to a family of lawyers. His affluent and cultivated
father was a prosecutor at the Parlement de Paris.The young man
received a very complete education, directed towards the study of
the sciences, at the Collège des Quatre Nations, presently
the Institut de France. It was there that he acquired the taste
and respect for precision: "I was accustomed to the rigorous
reasoning of mathematicians," he wrote. "They never take up a
proposition until the one preceding it has been solved. Everything
is connected, from the definition of the point and the line up to
the most sublime truths of transcendent geometry." (Archives of
the Académie des Sciences, Lavoisier Collection, ms.
He left the college in June 1761, forgoing the two years of philosophy that would have led to the title of bachelier, and on the advice of his father, began studying law. Graduating in 1764, he too began to practice at the Parlement de Paris. "Having reached philosophy, he conceived such a taste for the sciences that he decided to dedicate himself to them entirely." (Michaud, Biographie Universelle, article on Lavoisier written by Cuvier.)
Having been introduced to meteorology during secondary school by the Abbé de La Caille, he discovered other disciplines after his teacher's death in March 1762: botany at the Jardin du Roy, known today as the Jardin des Plantes, with Bernard de Jussieu (1699-1777); anatomy at the Medical School; electricity with the Abbé Nollet; mineralogy and geology with his father's friend, Jean Etienne Guettard (1715-1786), who had been elected to the Academy of Sciences in 1743 as a botanist and was the curator of the natural history collection belonging to the duc d'Orléans. The end result of this education was a gentleman, at ease in the practice of the sciences and the arts, possessing an open mind and a comprehensive curiosity, and capable of applying his reason to everything. His practical intelligence, working methods and sense of the concrete were those of a highly efficient organizer, an administrator and manager. Such a man had all the requisite qualities for becoming an outstanding "commis de l'Etat " (public servant), and it was precisely the itinerary he was going to follow at the General Farm, the Academy of Sciences and the Gunpowder and Saltpeter Administration.
Even if he did not practice his profession as a lawyer, he retained from it the love of the word and respect for precise language. His writings , somewhat formal in style, are always easy and pleasant to read because they are very clear and exact. Demonstrations are presented in a perfectly logical and didactic way. Moreover, they were always polished and rewritten several times, just like the briefs of a lawyer who understands the power of words. He took great care to present his discoveries with exactitude and refrained from borrowing from his competitors; he was never short of arguments to explain that he was unaware of their results, or else that the significance of their findings was different, which in fact was often the case. Regarding his own results, he never forgot to establish his intellectual ownership, by leaving sealed envelopes with the secretary of the Academy of Sciences, or by having him initial reports in the process of being written. Nevertheless, he did not always succeed - during his lifetime and even less so after his death - in preventing quarrels over precedence.
From Mineralogy to Geology
Lavoisier's interest in geology is reflected in the Atlas minéralogique de la France, Guettard's vast undertaking which had both theoretical and practical ends. It was to provide the duc d 'Orléans with maps showing all natural resources in the kingdom: "quarries, excavating mines, mineral springs, and all raw materials contained in the earth." (Lavoisier, Oeuvres , vol. V, p. 216.) In 1767, during the four months spent in the Vosges Mountains with Guettard, Lavoisier carried out a series of tests on mineral waters and observed the work of miners and metallurgists, all of which would nourish his reflections as a chemist. At the same time, he discovered the connection between geography, demography and economic activity. But it was geology which attracted him most. Starting from the works of his masters - Buffon (1707-1788), Guettard and Guillaume François Rouelle (1703-1770) -, he felt ready to construct a theory of the earth's formation. "There will result from this immense undertaking," he announced, "exact knowledge concerning the former boundries of the sea, the bed it occupied, and the former arrangement of the continents; in a word, a system based entirely on experiments and sound observations of the changes that have taken place on the earth." (Lavoisier, Oeuvres, vol. III, p. 109.)
The earth's crust, according to him, was formed from an old soil, composed of mountainous masses of granites poor in fossils, and a more recent one, fossiliferous and sedimentary. The rocks of the original soil, he wrote, "are arranged in perpendicular layers or inclined towards the horizon... They are composed of quartz, granite, shale, slate and talcose."(Lavoisier, Oeuvres, vol. V, p. 233.)
The deposits of the later soil were of four types: chalky (calcareous) soils and stones, gypseous soils and stones, pebbles of flint and clayey soils." (Lavoisier, Oeuvres, vol. V, p. 238.) In the beginning, he thought that a single period of sedimentation could account for the following phenomena: the complex arrangement of maritime basins and continents which had been determined by the receding waters of the primitive ocean; the pelagian layers, made up of almost pure calcaeous matter mixed with fragments of seashells accumulated over the centuries, which had formed out at sea; and the layers along the coast, which were of a more complex nature: at the top were pebbles, followed by coarse sand, fine sand, flint and, finally siliceous soil at the bottom. But in the autumn of 1766, a trip to Brie showed him that the alternation of calcareous and sandy layers was a much more frequent phenomenon than he had thought. And the theory left unexplained the coexistence of the coastal and pelagian layers. It had to be assumed that a cyclical movement of ebb and flow of the ocean had deposited a succession of sedimentary layers on the earth. To measure the thickness, altitude and extension of each of these geological stratum, Lavoisier attempted to establish barometric contour lines. But the technique proved to be insufficiently precise and it was through geodesic observations carried out with the protractor quarter-circle developed by Jean Charles de Borda (1773-1799) that he would subsequently check his data.
Meteorology was his second speciality. When he was twenty, he had begun making barometric observations in his residence on the rue du Four-Saint-Eustache, and he continued this activity all his life. In 1776, he carried out a comparative study of the lowest temperature observed during that winter (-14°) with that of the winter of 1709 (-15° 1/2); the data collected by the thermometer devised by Réamur (1683-1757) in 1732 were not in agreement with those obtained with more recent inventions: it was the occasion for him to define precise rules for the fabrication and graduation of thermometers and to deposit twelve standard models at the Academy of Sciences. In 1781, studying natural electricity and the formation of thunder, he demonstrated with Laplace and Volta that hydrogen, nitiric oxide, carbon dioxide and water vapor, in passing from the liquid to the vapor state emitted electrical charges measurable by the electrometer. With Benjamin Franklin (1706-1790), he installed lightening rods on the roof of Saint-Paul's Church.
He considered weather forecasting to be almost as difficult an art as medicine: one needed daily measurements of atmospheric pressure, the velocity and direction of winds at different altitudes and the hygrometric state of the air. He created a network of correspondents in France and Europe and selected barometers and wind gauges. "With all this information," he wrote, "it is almost always possible to predict one or two days in advance, within a rather broad range of probability, what the weather is going to be; it is even thought that it will not be impossible to publish daily forecasts which would be very useful to society." (Lavoisier, Oeuvres, vol. III, p. 771.)