Moonstone Research & Publications                                                         

Reaumur and His Thermometer.

Excerpt from R.L. Chambers' Book of Days, (Vol. 2) (1864) at 464-65

Rene Antoine Ferchault de Reaumur is an instance, among many, of those persons who, having devoted the greater part of their life's to scientific investigations, become known to posterity for only one, and that often a very subordinate achievement. Reaumur is now remembered almost exclusively by his thermometer: that is to say, his mode of graduating thermometers--a very small thing in itself. Yet in his day he occupied no mean place among French savans. From 1708, when he read his first paper before the Academy of Sciences, till his death on October 18, 1757, he was incessantly engaged in investigations of one kind or other. Geometrical speculations; the strength of cordage; the development of the shells of testaceous animals; the colouring-matter of turquoise-gems; the manufacture of iron, steel, and porcelain; artificial incubation; the imitating of the famous purple dye of the ancients; the graduation of thermometers; the reproduction of the claws of lobsters and crabs; the instincts and habits of insects--all in turn, engaged the attention of this acute and industrious man, and all furnished him with means for increasing the sum-total of human knowledge.

Scientific men, each in his own department, fully appreciate the value of Reaumur's labours; but to the world at large, as we have said, the thermometric scale is the only thing by which he is remembered. Almost precisely the same may be said of Fahrenheit. Had not the English persisted in using the graduation proposed by the last-named individual, his name would never have become a household word among us; and had not Reaumur's scale been extensively adopted on the continent, his more elaborate investigations,  buried in learned volumes, would have failed to immortalize his name.

Till the early part of the last century, the scales for measuring degrees of temperatures were so arbitrary, that scientific men found it difficult to understand and record each other's experiments; but Fahrenheit, in 1724, had the merit of devising a definite standard of comparison. He divided the interval between freezing water and boiling water into 180 equal parts or degrees, and placed the former at 32 degrees above zero or point of intense cold, so that the point of boiling-water was denoted by 212 degrees. It is supposed that the extreme cold observed in Iceland in 1709 furnished Fahrenheit with the minimum, or zero which he adopted in his thermometers; but such a limit to the degree of cold would be quite inadmissible now, when much lower temperatures are known to exist. Reaumur, experimenting in the same field a few years after Fahrenheit, adopted also the temperature of freezing water as his zero, and marked off 80 equal parts or degrees between that point and the temperature of boiling water. Celsius, a Swede, invented, about the year 1780, a third mode of graduation, called the Centigrade; in which he took the freezing of water as the zero point, and divided the interval between that and the point of ebullition into 100 parts or degrees. All three scales are now employed--a circumstance which has proved productive of an infinite amount of confusion and error. Thus, 212 degrees F. is equal to 80 degrees R. or 100 degrees C.; 60 degrees F. is equal to 12 and four-ninths degrees R., or seventeen and one-ninth degrees C.; and so on. Like the names of the constellations, it is difficult to make changes in any received system when it has become once established; and thus we shall continue to hear of Reaumur on the continent, and of Fahrenheit in England.

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Last modified: 01/17/05