Jacques Rohault

Jacques Rohault , born in 1618 (or perhaps towards the end of 1617) with Amiens and dead the December 27th 1672 with Paris, is a Physicien French which specified and popularized by remarkable experiments Cartesian physics and contributed to the decline of the Aristotélisme.

Biography

Jacques Rohault was the son of Ambroise Rohault, rich person commercial of wine of Amiens and marguillier of the Saint-Germain parish, and of Antoinette de Ponthieu. He made traditional studies at the Jésuites and learned the geometry as an autodidact. He is established mathematics professor in Paris. Its enthusiasm and its talents of popularizer attracted increasingly many customers to him: Claude Clerselier was his pupil; Bossuet obtained to him the load of mathematics professor and philosophy of the Dolphin, and he taught mathematics with princes de Conti. The matter of these courses was:

the first six books of Euclide
arithmetic the
spherical trigonometry and triangles
practical mathematics, i.e. geodesy, land surveying and the gauging
the fortifications
simple machines: winch, lever, corner
the drawing in perspective

He studied philosophy in Paris, perhaps with Clerselier, of which he married a girl, Genevieve, in 1663 after the death of his first wife, Nicole Filassier, and thus discovered the ideas of Descartes. He was member of the academy of Montmor. In December 1656, already famous, he repeated with Notre-Dame in the presence of a public many the barometric experiments that Blaise Pascal had made with the Tour Saint-Jacob.

In front of the multitude with its lessons, it organized at his place weekly public meetings, “Wednesdays of Rohault”, as from the following year. They were experiments with accompanying notes, often new and original, where its talents of experimenter and man of spectacle found to be expressed. Several testimonys show that it was familiar of the work of metals and glass, and thus near to the knowledge of craftsman: he liked certainly, known as Paul Mouy, “to penetrate the trade secrets”. Among the experiments which it gave to the public, one finds:

inspired by the Treated of Vuide of Blaise Pascal, of the original experiments showing gravity of the air;
inspired by the Meteors of Descartes, the experiments on the Dispersion of the light;
of personal research on curiosities of the time: the attraction of the magnets, Prince Rupert's drops.

These experiments proceeded in the following way: Rohault presented the phenomena in order to cause contradictory explanations on behalf of the public. Then, by against-experiments and a reasoning, it brought to its own conclusion. Malebranche testifies: “There was no safety to push it (...) because everyone knows with which accuracy and which force this scientist man pushed back the blows which one wanted to carry to him, and which with two or three words pronounced without heat and movement, it cut down the imagination of those which, very full with themselves, believed to cover it confusion”

These Wednesdays had an extraordinary success: “it was there people of any age, any sex and any condition”. By Rohault, Cartesian physics became with the mode and made fury in the living rooms.

As from 1664, Rohault is essential like the leader of Cartesian science. In 1667, having to organize the festivities which accompanied the return in France by ashes of Descartes, he imagined, not without skill, to make pronounce the second praise of the scientist by the canon Foucher, half-adversary of the Cartesianism.

The Treaty of physics (1671)

This work with exceptional success is distinguished from the former books of physique by the place given to the experimentation: the facts precede the explanations there. Although the subjacent ideas are essentially drawn from the Dioptrique and the Météores of Descartes, Rohault had the concern of explaining new phenomena: the Capillarity, the Magnetism.

The book comprises four parts:

the talk of the principles of physics, drawn from the Cartesian ideas on the extent and the movement. Rohault from of deduced the general laws from hydrostatic, optics, the deformation of the solids. Rohault develops a theory of the shock a little different from that of Descartes.
a cosmography, where Rohault, after having exposed the traditional doctrines (Ptolémée, Tycho Brahé) takes party for the system of Copernic.
a physicochemistry of the terrestrial elements: ground, air and water. Rohault particularly develops to with it a theory of the magnetization which, drawing aside the idea absurdity of remote action, rests on the intervention of a subtle matter made up of “particles screw” and “particles nuts”.
a detailed study of the movement of the “animated bodies”, i.e. principles of the alive one. There Rohault follows still generally Descartes, but prefers the theory of Harvey for the blood circulation and the operation of the cardiac muscle.

The Traité of Physics appeared in Latin translation with Geneva in 1674. On the initiative of John Clarke, another Latin translation appeared with London in 1702, which knew five republications.

By Rohault, Cartesian physics remained until 1730 in the mechanist spirit, rather than by metaphysics.

Talks on philosophy (1672)

In front of the attacks of the Church against the ideas of Descartes (decree of the Congregation of the Index of November 20th, 1663), Rohault, chief of school of the Cartesianism, defended in Entretiens the teaching of the Master on two points:

the Transsubstantiation;
the heart of the animals, where the author turns over against his adversaries the charge of Matérialisme.

The work did not make large - thing for the cause, and attracted as of its publication a series of Calomnie S against Rohault, which died shortly after. The authorities required of him, in its last moments, a catholic profession of faith in due form.

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