its huge teeth, roamed over Europe in the last geological age, and its teeth, covered with a very strong enamel, have been preserved in strata, or in fissures. Under the influence of the chemical action going on in rocks, the enamel becomes occasionally coloured, so as to resemble a turquoise-coloured porcelain. This was evident to Réaumur, who wrote upon the fact. Other studies took him away from natural history for a while, but they certify to the energy and hard work of the man and his great accuracy. Réaumur’s experiments in the manufacture of iron and steel were of great importance, and it was an attempt to get the art of making steel introduced into France, that urged him on. He made good use of his knowledge, for on publishing his methods of work, the Regent gave him a pension of 12,000 livres a year. Next he discovered the art of tinning iron, and whilst experimenting, Réaumur first noticed that many metallic substances in passing from the heated fluid condition to the cold state, have a tendency to assume particular geometrical or crystalline forms. Among his useful discoveries were plans for the manufacture of porcelain, and they were of great use to France. A thermometer, with a scale of temperature, still largely used in some parts of the world, was invented by him, and he took the freezing and boiling points of water as fixed points, and divided the interval into eighty degrees. The present centigrade thermometer used in France is made on the same plan, but the interval is divided into one hundred degrees. Labouring as a physicist, still all this time Réaumur was doing wonderful work in zoology. He described the means by which many echinodermata—sea-urchins and sea-stars—execute their movements, and discovered the curious manner in which many crustacea, such as crabs and lobsters, throw off their limbs and repair them. But his real and lasting work was on insects, which occupied all his best and later years. Living in perfect quietude, without any great worries, sometimes at his estate at Saurlonge, and at other times at Bercy, near Paris, he worked on, giving all his energies to his subject. His labours, he stated, were published with a view to assist future investigators, and most of them were original. He kept up his pretty country house and garden, and observed the insects and their habits, and especially their methods of changing form. He followed Swammerdam in these investigations, and although there are some differences of opinion between the two great men, still they both made their mark in the investigation of that part of natural history which deals with the progressive development of the minute young to the full-grown creature. Réaumur was sufficiently wealthy to form a large collection of animals, and a very able man, M. Brisson, was employed by him as its curator, and was allowed to describe the quadrupeds and birds. Réaumur did not care so much about classifying