JOURNAL oa CREMICAL EDUCATION
320
Mnncn, 1927
THE LIFE OF EDME MARIOTTE* LunwIG DARMSTAEDTBR, PREUSSISCAB STAAXSBIBLIOTHEK BERLIN, GERMANY We owe the great men of science not only a careful reading of their works but also a study of their lives and characters so that they may appear to us as real personalities. We can then better understand how they came to undertake and accomplish their tasks and appreciate in what way their achievements reacted in determining the course of their careers. Practically nothing is known about the lives of many of our intellectual giants and we are forced to construct our notions of the motives which influenced their careers from a consideration of their writings. This is especially true of Edme Mariotte. The existing records contain so little concerning his life, that even the year and place of his birth are uncertain. The mathematician, Marie Jean de Condorcet, in his "Eulogies of the Academicians 1666-1699," considered Mariotte's accomplishments worthy of praise, but he knew nothing to record concerning the circumstances of his life, although only one hundred years had elapsed since his death. Today, after the passage of three hundred years, we are perforce compelled to judge him from his writings alone. The most important of his works known to us deals with the Law of Mariotte, which is better designated as the Boyle-Mariotte Law, since Robert Boyle took an active part in its establishment. This law states that the volume of a given mass of gas varies inversely with the pressure impressed on it. In the paper entitled "Sur la nature de l'air," read in 1676 and included in "Histoire de l'Academie," page 176 (published 1733). Mariotte says, "Air expands and contracts according to the weight resting on it," and he illustrated this statement by a simple experiment. "I took a tube 40 inches long and poured into it 27'/% inches of mercury, so that 1Z1!2 inches of air were in the tube. I now inverted the tube and plunged it one inch deep into mercury. The column of mercury fell and came to rest a t a height of 14 inches, that is, at one-half the height of the ordinary air pressure of 28 inches. The enclosed air occupied the upper part of the tube, amounting to 25 inches; its volume doubled since it originally had occupied only 12'/% inches. Boyle had previously discovered this relation between volume and pressute in 1600 and had demonstrated it by a simple experiment. "He enclosed 12 cubic inches of air in the shorter arm of a bent tube by means of a mercury seal. He then poured mercury into the longer arm and the enclosed air was compressed in the same measure as the mercuy was added. With double the original quantity of mercury, the volume of the air was 6 cubic inches; with triple the quantity of mercury, the volume * Translated at the author's request by Ralph E. Oesper. University of Cincinnati, Cincinnati. Ohio.
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was 4 cubic inches; or the air was compressed in direct ratio to the compressing force." Mariotte was also perfectly clear in his ideas about air pressure and its dependence on the height above the surface of the earth. The famous experiment carried out by Pascal's brother-in-law, Perier, on the Puys de Dome in 1648, had only shown that the air pressure varies with altitude. Mariotte pointed out that the fall of the mercury column might be used as a measure of altitude and recommended that the barometer be used for this purpose. He stated that an ascent of 60 feet caused the mercury to fall about one division on his scale. Edme Mariotte is thought to have been born in Dijon about 1620 and was destined for the clergy in his early youth. Nothing is known about his education, but he seems to have risen to eminence quite early for he was prior of the monastery of St. Martin sous Beaune near Dijon when the Academie des Sciences was founded by Colbert in 1666. It appears from the "Histoire de l'Acadamie Royale des Sciences" that he was unusually active as a member and, up to the middle of 1683,he seldom missed a meeting and was interested in the most diverse subjects presented to that body. This activity indicates that his position as prior was merely a benefice, and Mariotte seemed to have spent most of his time in Paris pursuing his scientific studies. One of his earliest investigations, that on the eye, was presented before the Academy in 1669. He found that the entrance of the optic nerve, the pupilla optica, or the blind spot, was not exactly in the center line of the eye, but was situated somewhat higher and closer t o the nose. Simple experiments showed him that a round piece of paper fixed to another whose image fell on the blind spot, disappeared when both were observed with only one eye. In the antero-posterior axis of the eye, he observed a thinner portion colored yellow and hence known as the yellow spot, and he regarded this as the light sensitive region. This discovery, although much doubted, later was proved to be correct. The blind spot is often known as Mariotte's spot. In 1674 Mariotte developed the laws of percussion and the type of apparatus which he devised for detecting shocks is still used. His treatise on the nature of colo~s,presented before the Academy in 1679, is of great interest and in the history of that organization, it is stated: "Such studies were particularly suited to Mariotte because he was unusually keen in his observations and he performed experiments just as expertly as he devised them." In this paper he offered an explanation of the halos and rings seen around the sun and moon in misty weather, and said that the greater halos were produced by double refraction and simple retlection in the ice crystals of the upper layers of the earth's atmosphere. This explanation is still accepted. He also included a note
on radiant heat to which Melloni referred later. Mariotte observed that the sun's rays passed through transparent bodies without noticeable weakening, while most of the rays from a fire, although not so hot, are reflected. Condorcet said of him, "Few investigators have shown, in their writings, a more upright and disinterested love of the truth than did Mariotte." This was true of all the instances cited above and also applies to his studies of hydrostatics and hydraulics, presented in 1669 before the Academy, and published in 1717, after Mariotte's death, by Philippe de la Hire, to whom they were entrusted in the first days of Mariotte's last illness. Moritz Riihlmann, in his text on technical mechanics, regards them as the first worthwhile measurements of the velocity of water flowing in rivers, canals, and from emptying vessels, of the movement of water in pipes, of jets of water, and the impact of moving water. In addition, while calculating the strength of the walls of pipes, he treated the bursting strength of prismatic bodies more correctly than had Galileo before him. Mariotte died May 12, 1684, in Paris. In that year he had clearly demonstrated, by experiments and statistics, the meteorological source of water issuing from springs, and he also devised the Mariotte flask, the purpose of which is to permit the exit of large masses of water without change of pressure.
