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Renι-Antoine Ferchault de Reaumur
(28 Feb 1683 - 18 Oct 1757)

French entomologist and physicist with diverse interests. His name remains known for the temperature scale he devised. He studied the manufacture of iron, steel and porcelain. In biology he investigated gastric juices, and the regeneration of the lost limbs of crayfish, as well as writing a six-volume natural history of insects.

Renι Reaumur - Biography

From The General Biographical Dictionary (1816)

Rene Reaumur

[p.91] REAUMUR (Renι Anthony Farchault, Sieur de), an eminent French naturalist, was born at Rochelle in 1683. He learned grammar at the place of his birth, and studied philosophy at the Jesuits college at Poitiers. In 1699 he went from thence to Bourges, at the invitation of an uncle, where he studied the civil law. In 1703, he went to Paris, and applied himself wholly to the mathematics and natural philosophy ; and in 1708, being then only twenty-four years old, he was chosen a member of the Royal Academy of Sciences ; and during that and the following year, he described a general method of finding and ascertaining all curves described by the extremity of a right line, the other end of which is moved round a given curve, and by lines which fall upon a given curve, under a certain angle greater or less than a right angle.

These are the only geometrical performances that he produced. In the year 1710 he read his observations upon the formation of shells, in which he proved that they grow not like the other parts of the animal body, by expansion, but by the external addition of new parts : he also assigned the cause of the variety of colour, figure, and magnitude which distinguishes one shell from another. During the experiments which this inquiry led him to make upon the snails, he discovered a very singular insect which lives not only upon these animals, but burrows in their bodies, a situation which he never leaves unless he is forced out of it by the snail. This inquiry also gave occasion to M. Reaumur to account for the progressive motion of testaceous animals of different kinds, and to describe and explain an almost endless variety of organs which the author of nature has adapted to that purpose. He produced also the same year the natural history of cobwebs. M. Bon, the first president of the chamber of accounts at Montpellier, had shewn that cobwebs might be spun into a kind of silk, which might be applied to useful purposes ; but it was still necessary to determine whether spiders could be bred in sufficient numbers, without an expence too great for the undertaking to bear ; and Reaumur soon found that M. Bon's discovery was a mere matter of curiosity, and that the commercial world could derive no advantage from cobwebs.

[p.92] It had been long known, that marine animals adhere to solid bodies of various kinds, either by an attachment which continues during their existence, or which they can determine at pleasure ; but how this attachment was formed, remained a secret, till it was discovered by Reaumur, to whose inquiries we are indebted for our knowledge of many organs and materials adapted to that purpose, before unknown. In the course of this inquiry, M. Reaumur discovered a fish different from that which furnished the ancients with their Tyrian dye, but which has the same property in a yet greater degree : upon the sides of this fish there are small grains, like those of a hard roe, which being broken, yield first a fine full yellow colour, that upon being exposed for a few minutes to the air, becomes a beautiful purple.

About the same time Reaumur made a great variety of experiments to discover whether the strength of a cord was greater or less than the sum of the strength of the threads of which it consists. It was generally believed that the strength of the cord was greater, but Reaumur's experiments proved it to be less ; whence it necessarily follows, that the less a cord differs from an assemblage of parallel threads, i. e. the less it is twisted, the stronger it is*.

It had been long asserted by those who lived on the sea coast, or the banks of great rivers, that when craw-fish, crabs, and lobsters, happen to lose a claw, nature produces another in its stead : this, however, was disbelieved by all but the vulgar, till Reaumur put the matter out of dispute, and traced the re-production through all its circumstances, which are even more singular than the thing itself. M. Reaumur also, after many experiments made with the torpedo, or numb-fish, discovered that its effect was not produced by an emission of torporific particles, as some have supposed, but by the great quickness of a stroke given by this fish to the limb that touches it, by muscles of a most admirable structure, which are adapted to that purpose. These discoveries, however, are chiefly matters of curiosity ; those which follow are of use.

It had long been a received opinion, that Turquoise stones were found only in Persia ; but Reaumur discovered mines of them in Languedoc ; he ascertained the degree of heat necessary to give them their colour, and the [p.93] proper form and dimension of the furnace ; he proved also that the Turquoise is no more than a fossil bone petrified, coloured by a metallic solution which fire causes to spread ; and that the Turquoises of France are at least equal in beauty and size to those of the East. He also discovered the secret of making artificial pearls, and of the substance necessary to give them their colour, which is taken from a little fish called able, or ablette. He drew up, at the same time, a dissertation upon the true pearl, which he supposed to be a morbid concretion in the body of the animal.

Reaumur soon after published the History of the Auriferous rivers of France, in which he has given a very particular account of the manner of separating the grains of gold from the sand with which it is mixed. Among other memoirs he drew up the following : 1. Concerning the vast bank of fossil shells, which, in Touraine, is dug for manure called Falun : 2. Upon flints, proving that they are only more penetrated by a stony juice ; or, if the expression may be allowed, more stonified than other stones, though less than rock crystal. 3. Upon the Nostoch, a singular plant, which appears only after hard rains in the summer, under a gelatinous form, and soon after disappears. 4. Upon the light of Dails, a kind of shell fish, which shines in the dark, but loses its lustre as it grows stale. 5. Upon the facility with which iron and steel become magnetic by percussion.

In 1722, he published a work under the title of “The art of converting Iron into Steel, and of rendering cast Iron ductile.” The use of iron is well known under the three forms of cast iron, forged or bar iron, and steel : iron in the first state is susceptible of fusion, but it is brittle and hard, and can neither be forged by the hammer, nor cut by the chissel : in the second state it is malleable, and may be both filed and cut, but it is no longer fusible without the addition of a foreign substance : in the third it acquires a very singular property of becoming hard and brittle, if after it has been made red hot it is dipped into cold water : the extreme brittleness of cast iron makes it unfit for the construction of any thing that is required to be either supple or elastic, and still more for any thing upon which it will be necessary to employ a tool of any kind after it comes out of the font, for no tool can touch it. On the other hand, the manner of converting forged, or bar-iron into steel, was then wholly unknown in France. But Reaumur [p.94] having, in the course of other inquiries, found that steel differed from iron only in having more sulphur and more salt in its composition, undertook to discover the method of giving to iron what was wanting to make it steel, and at length perfectly succeeded, so as to make steel of what quality he pleased.

The same experiments which convinced Reaumur that steel differed from iron only in having more sulphur and salt, convinced him also that cast iron differed from forged iron, only by having still more sulphur and salt than steel ; it was steel with an excess of its specific difference from forged iron, : he therefore set himself to take away this excess, and he succeeded so as to produce a great variety of utensils in cast iron, which were as easily wrought as forged iron, and did not cost half the money. However, a manufactory set on foot in France for rendering cast iron sufficiently ductile to be forged and wrought, was, after some time, discontinued. For discovering the secret of converting iron into steel, the duke of Orleans, being then regent, settled a pension upon Reaumur of 12,000 livres a year, and, at his request, it was settled upon the academy after his death, to be applied for defraying the expences of future attempts to improve the arts.

M. de Reaumur also discovered the secret of tinning plates of iron, as it was practised in Germany ; and his countrymen, instructed in that useful manufacture, no longer imported them from abroad. He has likewise the credit of having invented the art of making porcelain. A few simple observations upon fragments of glass, porcelain, and pottery, convinced him that china was nothing more than a demi-vitrification ; now a demi-vitrification may be obtained either by exposing a verifiable matter to the action of fire, and withdrawing it before it is perfectly vitrified, or by making a paste of two substances, one of which is vitrifiable, and the other not : It was therefore very easy to discover by which of these methods the porcelain of China was made ; nothing more was necessary than to urge it with a strong fire : if it consisted wholly of a vitrifiable matter half vitrified, it would be converted into glass ; if of two substances, one of which was not verifiable, it would come out of the furnace the same as it went in : this experiment being made, the China porcelain suffered no alteration, but all the European porcelain was changed intp glass.

[p.95] But when the China porcelain was thus discovered to consist of two distinct substances, it was farther necessary to discover what they were, and whether France produced them. M. Reaumur accomplished these desiderata, and had the satisfaction to find that the materials for making China porcelain were to be had in France, in the same abundance, and in greater perfection, than in India. Reaumur also contrived a new species of porcelain, consisting only of glass, annealed a second time, with certain easy precautions, which, though less beautiful than other porcelain, is yet a useful discovery, considering the great facility and little expence with which it is made.

M. Reaumur was the first that reduced thermometers to a common standard, so as that the cold indicated by a thermometer in one place, might be compared with the cold indicated by a thermometer in another ; in other words, he prescribed rules by which two thermometers might be constructed that would exactly coincide with each other through all the changes of heat and cold : he fixed the middle term, or zero, of his division of the tube, at the point to which the liquor rises when the bulb is plunged in water that is beginning to freeze ; he prescribed a method of regulating the divisions in proportion to the quantity of liquor, and not by the aliquot parts of the length of the tube ; and he directed how spirits of wine might be reduced to one certain degree of dilatability. Thermometers constructed upon these principles were called after his name, and soon took place of all others.

Reaumur also invented the art of preserving eggs, and of hatching them ; this art had been long known and practised in Egypt, but to the rest of the world was an impenetrable secret : he found out and described many ways of producing an artificial warmth in which chickens might be hatched, and some by the application of fires used for other purposes ; he shewed how chickens might be hatched in a dunghill, he invented long cages in which the callow brood were preserved in their first state, with fur cases to creep under instead of the hen, and he prescribed proper food for them of things every where to be procured in great plenty. He found also that eggs might be kept fresh and fit for incubation many years, by washing them with a varnish of oil, grease, or any other substance, that would effectually stop the pores of the shell, and prevent the contents from evaporating ; by this contrivance eggs may not [p.96] only be preserved for eating or hatching in the hotest climates, but the eggs of birds of every kind may be transported from one climate to another, and the breed of those that could not survive a long voyage, propagated in the most distant part of the world.

While he was employed in these discoveries, he was gradually proceeding in another work, the “History of Insects,” the first volume of which he published in 1734. This volume contains the history of caterpillars, which he divides into seven classes, each of a distinct kind and character : he describes the manner in which they subsist, as well under the form of caterpillars as in the chrysalis ; the several changes which they undergo ; the manner of taking food, and of spinning their webs. The second volume, which was published in 1736, is a continuation of the same subject, and describes caterpillars in their third state, that of butterflies, with all the curious particulars relating to their figure and colour, the beautiful dust with which they are powdered, their coupling, and laying their eggs, which the wisdom of Providence has, by an invariable instinct, directed them to do, where their young may most conveniently find shelter and food. The third volume contains the history of moths, not only of those which are so pernicious to clothes and furniture, but those which live among the leaves of trees, and in the water ; the first is perhaps the most useful, because Reaumur has given directions how the cloth-moth may be certainly destroyed ; but the second abounds with particulars that are not only curious, but wonderful in the highest degree. This volume also contains the history of the vine-fretter, an insect not less destructive to our gardens than the moth to our furniture, with an account of the worm that devours them, and the galls produced upon trees by the puncture of some insect, which often serve them for habitations.

From the gall, or gall-nut, properly so called, Reaumur proceeds, in his fourth volume, to the history of those protuberances which, though galls in appearance, are really insects, but condemned by nature to remain forever fixed and unmoveable upon the branches of trees ; and he discloses the astonishing mystery of their multiplication. He then proceeds to give an account of flies with two wings, and of the worms in which they pass the first part of their lives ; this article includes the very singular history of the gnat. The fifth volume treats of four-winged flies, and [p.97] among others of the bee, concerning which he refutes many groundless opinions, and establishes others not less extraordinary.

The bee is not the only fly that makes honey, many species of the same genus live separate, or in little societies. The history of these begins the sixth and last volume, and contains a description of the recesses in which they deposit and secure their eggs, with proper nourishment for the worms they produce till their transformation. The author then proceeds to the history of wasps, as well those who live separate, as in companies, to that of the lion-pismire, the horse-stinger, and lastly, to the fly called an ephemeron, a very singular insect, which, after having lived in the water three years as a fish, lives as a fly only one day, during which it suffers its metamorphosis, couples, lays its eggs, and leaves its dead carcass upon the surface of the water which it had inhabited. To this volume there is a preface, containing the discovery of the polype, an animal that multiplies without coupling, that moves with equal facility upon its back or its belly, and each part of which, when it is divided, becomes a complete animal, a property then thought singular, but since found to be possessed by several other animals.

It had long been a question amongst anatomists, whether digestion is performed by solution or trituration : M. de Reaumur, by dissecting a great number of birds of different kinds, and by many singular experiments, discovered that the digestion of carnivorous birds is performed by solution, without any action of the stomach itself upon the aliments received on it ; and that, on the contrary, the digestion of granivorous birds is effected wholly by grinding or trituration, which is performed with a force sufficient to break the hardest substances.

M. de Reaumur, during the course of his experiments upon birds, remarked the amazing art with which the several species of these animals build their nests. His observations on this subject he communicated to the French academy in 1756, and this memoir was the last he exhibited. He died by a hurt in his head, received from a fall at Bermondiere in the Maine, upon an estate that had been left him by a friend, on the 17th of October, 1756, aged seventy-five years.

He was a man of great ingenuity and learning, of the [p.98] strictest integrity and honour, the warmest benevolence, and the most extensive liberality.

* That mode of uniting various threads into a cord, is undoubtedly the best which causes the tensions of the threads to be equal in whatever direction the cord is strained.

Text from Alexander Chalmers (ed.), The General Biographical Dictionary (1816), Vol. 26, 91-98. (source) . Image, from another source: Engraving by Johann-Martin Bernigeroth (1713-1767) (source) .

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