added to them. Lavoisier turned his attention to the defects of the existing theory about 1770; and the last-named experiments probably directed him more specifically to the essential point of the inquiry. He pursued his researches with unwearied industry; and by a long series of experiments of the most laborious and precise nature, he succeeded in determining that, in all cases of combustion, that substance which is the real combustible invariably receives an addition, or enters into a new combination; and the matter with which it combines is in all cases that same substance which had now been shown by Priestley to be one of the constituents of the atmosphere, and which was then known by the name of vital air.

It was however long before Lavoisier gained a single convert. At length M. Berthollet, at a meeting of the Academy in 1785, publicly renounced the old opinions and declared himself a convert. Fourcroy followed his example. In 1787, Morveau, during a visit to Paris, became convinced, and declared the conclusions of Lavoisier irresistible. The younger chemists speedily embraced the new views; and their establishment was thus complete. There only remained some lurking prejudices in England, where the Essay of Kirwan retained its credit. Lavoisier and his coadjutors translated this essay into French, accompanying each section by a refutation. So completely was this done, that the author himself was convinced; and, with that candour which distinguishes superior minds, gave up his views as untenable, and declared himself a convert.

These discoveries introduced Lavoisier to the notice of the most eminent persons in the State; and in 1776 Turgot engaged him to superintend the manufacture of gunpowder for the Government. He introduced many valuable improvements in the process, and many judicious reforms into the establishment.

and this conviction, joined with a full perception of the immense benefits accruing from personal acquaintance among men of kindred pursuits, and the interchange of social good offices, led him to the regular practice of opening his house on two evenings in every week, for an assembly of all the scientific men of the French capital; which very soon became a point of general resort and reunion to the philosophers of Europe.

At these meetings general discourse and philosophic discussion were agreeably intermingled; the opinions of the most eminent philosophers were freely canvassed; the most striking and novel passages in the publications of foreign countries were made known, recited, and animadverted upon; and the progress of experiment was assisted by candid comments and comparison with theory. In these assemblies might be found, mingling in instructive and delightful conversation, all those whose names made the last century memorable in the annals of science. Priestley, Fontana, Landriani, Watt, Bolton, and Ingenhouz, were associated with Laplace, Lagrange, Borda, Cousin, Monge, Morveau, and Berthollet. There was also an incalculable advantage in bringing into communication and intimacy men engaged in distinct branches of science: the intercourse of the mathematician with the geologist, of the astronomer with the chemist, of the computer with the experimenter, and of the artist with the theorist, could not fail to be of mutual advantage. In no instance were the beneficial effects of such intercourse more strikingly displayed than in the chemical sciences; which, from this sort of comparison of ideas and methods, began now to assume a character of exactness from an infusion of the spirit of geometry; and a department hitherto abandoned to the wildest speculations, and encumbered with the most vague and undefined

phraseology (derived from the jargon of the alchymists), began to assume something like arrangement and method in its ideas, and precision and order in its nomenclature. This influence was strongly marked in the physical memoirs produced in France from this period downwards. The precision and severity of style, and the philosophical method of the mathematicians, was insensibly transfused into the papers of the physical and chemical philosophers.

Lavoisier individually profited greatly by the sources of improvement and information thus opened. Whenever any new result presented itself to him, which, perhaps, from contradicting all received theories, seemed paradoxical, or at variance with all principles hitherto recognised, it was fully laid before these select assemblies of philosophers; the experiment was exhibited in their presence, and they were invited with the utmost candour to offer their criticisms and objections. In perfect reliance on the mutual spirit of candour, they were not backward in urging whatever difficulties occurred to them, and the truth thus elicited acquired a firmness and stability in its public reception proportioned to the severity of the test it had undergone. Lavoisier seldom announced any discovery until it had passed this ordeal.

At length he combined his philosophical views into a connected system, which he published in 1789, under the title of Elements of Chemistry:' a beautiful model of scientific composition, clear and logical in its arrangement, perspicuous and even elegant in its style and manner. These perfections are rarely to be found in elementary works written by original discoverers. The genius which qualifies a man for enlarging the boundaries of science by his own inventions and researches is of a very different class from that which confers the ability to elucidate, in a simple and systematic course, the order and connexion of

elementary truths. But in Lavoisier these different species of talent were most happily blended. He not only added profound truths to science, but succeeded in adapting them to the apprehension of students, and was able to render them attractive by his eloquence.

In 1791 he entered upon extensive researches, having for their object the application of pneumatic chemistry to the advancement of medicine, in reference to the process of respiration. With this view he examined in great detail the changes which the air undergoes, and the products generated in that process of the animal economy. He had previously, however, as far back as 1780, detailed a series of experiments to determine the quantity of oxygen consumed and carbonic acid generated by respiration, in a given time, in the Memoirs of the French Academy.

In the twenty volumes of the Academy of Sciences, from 1772 to 1793, are not less than forty memoirs by Lavoisier, replete with all the grand phenomena of the science:-the doctrine of combustion in all its bearings; the nature and analysis of atmospheric air; the generation and combinations of elastic fluids; the properties of heat; the composition of acids; the decomposition and recomposition of water; the solutions of metals; and the phenomena of vegetation, fermentation, and animalisation. These are some of the most important subjects of his papers; and during the whole of this period he advanced steadily in the course which was pointed out to him by the unerring rules of inductive inquiry, to which his original genius supplied the commentary. So well did he secure every point of the results to which he ascended, that he never made a false step. It was only in one subject, before alluded to, that he may be said to have gone a few steps too far. Nor did he ever suffer himself to be discouraged, or his ardour to be damped by the difficulties and obstacles which perpetually

impeded his progress. He traced new paths for investigation, and founded a new school of science; and his successors had ample employment in following out the inquiries which he had indicated, and exploring those recesses to which he had opened the way.

In the relations of social and civil life Lavoisier was exemplary; and he rendered essential service to the state in several capacities. He was treasurer to the Academy, and introduced economy and order into its finances: he was also a member of the board of consultation, and took an active share in its business. When the new system of measures was in agitation, and it was proposed to determine a degree of the meridian, he made accurate experiments on the dilatation of metals, in conjunction with Laplace (1782), to ascertain the corrections due to changes of temperature in the substances used as measuring rods in those delicate operations.

By the National Convention he was consulted on the means of improving the manufacture of assignats, and of increasing the difficulty of forgery. He turned his attention to matters of rural economy, and, by improved methods of cultivation, on scientific principles, he increased the produce of an experimental farm nearly one half. In 1791 he was invited by the Constituent Assembly to digest a plan for simplifying the collection of taxes: the excellent memoir which he produced on this subject was printed under the title of The Territorial Riches of France.' 6 He was likewise appointed a Commissioner of the National Treasury, in which he effected some beneficial reforms.

During the terrors of Robespierre's tyranny, Lavoisier remarked that he foresaw he should be stripped of all his property, and accordingly would prepare to enter the profession of an apothecary, by which he