Reaumur Avas a man of wide attainments and great industry. His writings, sometimes on trivial topics, were frequently diffuse, yet always interesting. His mind was original and intensely practical. As a rule he avoided theoretical questions, but Avhen he took them up his manner of treatment Avas remarkably clear, chiefly on account of an ingenious use of metaphor, often expanding into allegory. His memory Avas retentive, his information immense, and his kindliness of disposition such that his knowledge and wealth seemed to be amassed only for the benefit of his friends. He always bore a high character, was a great favourite in society, and associated on terms of intimacy Avith the principal great men of the time in Europe.

Reaumur’s scientific papers are too numerous to be recapitulated; they deal with nearly all branches of science. His first paper, in 1708, was on a general problem in geometry, his last, in 1756, on the forms of birds’ nests. He proved experimentally the fact, afterwards demonstrated theoretically by Du Hamel, that the strength of a rope is less than the sum of the strengths of its separate strands. He examined and reported on the auriferous rivers, the turquoise mines, the forests, and the fossil beds of France. He devised the method of tinning iron that is still employed, and investigated the differences betAveen iron and steel, correctly slioAA'ing that the amount of combustible matter (sulphur in the language of the old chemistry) is greatest in cast iron, less in steel, and least in Avrought iron. His book on this subject (1722) Avas translated into English and German. The thermometer by Avhich he is noAv best remembered Avas constructed on the principle of taking the freezing-point of water as 0°, and graduating the tube into degrees each of which Avas one-thousandth of the volume contained by the bulb and tube up to the zero mark. It Avas purely an accident dependent on the dilatability of the particular quality of alcohol employed which made the boiling-point of Avater 80°; and mercurial thermometers the stems of which are graduated into eighty equal parts between the freezing and boiling points of water are not Reaumur thermometers in anything but name.

Reaumur Avrote much on natural history. Early in life ho described the locomotor system of the Echinodermata, and shoAved that the supposed vulgar error of Crustaceans replacing their lost limbs Avas an actual fact. In 1710 he Avrote a paper on the possibility of spiders being used to produce silk, which Avas so celebrated at the time that the Chinese emperor Kang-he caused a translation of it to be made. He treated also of botanical and agricultural matters, and devised processes for preserving birds and eggs. He elaborated a system of artificial incubation, and made important observations on the digestion of carnivorous and graminivorous birds; but his greatest work is the Mémoires pour servir à l’Histoire des Insectes, 6 vols., with 267 plates, Amsterdam, 1734-49. It describes the appearance, habits, and locality of all the knoAvn insects except the beetles, and is a marvel of patient and accurate observation. Amongst other important facts stated in this work are the experiments which enabled Reaumur to prove the correctness of Peyssonel’s hypothesis, that corals were animals and not plants, as AA׳as previously supposed.