CHARLES STEPHEN LOUIS, a mathematician and mechanician, born at Cressy en Brie, near Meaux, the 25th August 1699, son of Stephen Camus, a surgeon of that town, and Margaret Maillard.

His taste for practical mechanics was very early demonstrated by a singular ingenuity in the construction of a variety of little machines with which he amused himself; and he soon felt so strongly the value of mathematical studies, that he urged his parents to find the means of sending him to a school where he might apply to them. In compliance with his wishes, he was placed, when he was little more than ten years old, at the Collège de Navarre in Paris; and in two years he acquired knowledge enough to become an instructor of others, and to relieve his friends from all further expense in his education. He was assisted in the pursuit of the higher departments of the mathematics by the celebrated M. Varignon; and he particularly applied himself to civil and military architecture, and to astronomy.

The first result of his studies that was destined for the public eye, was an essay On the Masts of Ships, a subject which had been proposed in 1727 as a prize question by the Academy of Sciences. This essay was received with considerable approbation, and was inserted in the second volume of the Collection of Prize Memoirs. Shortly after, the author was made an adjunct or sub-associate of the academy, in the department of mechanics.

In 1728 he brought forward a memoir on the Living Force of bodies in motion, in which he concludes, from considering the action of springs and other similar powers, that its true measure is the product of the mass into the square of the velocity, as Leibnitz maintained; this product being also proportional to that of the force into the space through which it acts, while the momentum is proportional to the force and the time conjointly. In December 1730 M. Camus was appointed professor of geometry to the Academy of Architecture, and a few years afterwards he became secretary to the same body.

The Memoirs of the Academy for 1732 contain a short paper on a Problem proposed by M. Cramer, respecting the determination of two curves bearing a particular relation to each other. It was the custom of the age to consider exercises of this sort as trials of strength, to which it was incumbent on all geometricians to submit, for the honour of the countries in which they lived, and of the societies to which they belonged. The author was elevated in 1733 to the rank of an associate of the academy, together with Clairaut, over whom he even obtained some advantage in the ballot.

He communicated to the academy, in the same year, a valuable paper on the Teeth of Wheels. La Hire had already laid the foundation of the investigation on its true basis, and had pointed out the use of different epicycloidal curves for the forms of the teeth of wheels in different circumstances; and M. Camus in this essay enters into some further inquiries, particularly with regard to the best proportions for the length of the teeth, and the comparative diameters of the wheels; a discussion for which his intimate acquaintance with the art of the clockmaker made him particularly well qualified. In 1736 he accompanied Maupertuis and Clairaut in the expedition to Lapland, for the measurement of a degree of the meridian; and he was enabled to render them very essential service, not only as a geometrician and an astronomer, but also by his skill in various departments of the mechanical arts, which became particularly valuable in so remote a situation.

M. Camus directed his attention in 1738 to the well known but interesting mechanical phenomenon of a pistol ball piercing an open door without causing any very sensible motion in the door, and published a paper on the subject in the Memoirs of the Academy. He justly observes, that the effect of any force depends, not only on its magnitude, but also on the time for which it operates; and that though the impulse of the ball must tend to carry the door before it with a force paramount to the resistance which it opposes to the ball, yet the time of the action of this force is too short to produce a sensible effect on the whole mass of the door.

In 1739 he presented to the academy two hydraulic memoirs, the one on Water Buckets, the other on Pumps. In the latter he investigates the diameter of a valve capable of transmitting the greatest quantity of water within a given barrel; a valve which is too large not being at liberty to rise to a sufficient height.

He inserted in the Memoirs for 1740 a confutation of a Mechanical Fallacy, which has misled many of the enthusiasts who have bewildered themselves in the search of a perpetual motion; demonstrating that when a number of weights are caused to descend, in any imaginable paths, at a greater distance from the centre of a wheel than they ascend, the number of the weights descending at any one time must always be smaller than those of the weights ascending, and in such a proportion as perfectly to compensate for the mechanical advantage apparently gained by the greater distance. In the following year he was received into the number of the academicians in the department of geometry, on occasion of the resignation of M. Fontenelle. He published also, in the Memoirs for 1741, an account of a Gauging Rule for measuring barrels of different forms, by simple inspection of the logarithmic scales engraved on it, observing only some easy rules for their adjustment, according to the general nature of the solid. In 1746 he presented a report, in conjunction with M. Hellot, on the Length of the Standard Ell, which was thought worthy of being inserted in the collection of the academy.

We find among the Memoirs for 1747 an essay of M. Camus on the Tangents of Curves having several branches crossing each other, which frequently require for their determination the use of fluxions of the higher orders, the first fluxions of the absciss and ordinate vanishing together. M. Saurin had before given a similar solution of the problem, but had not attempted to explain the metaphysical ground upon which the apparent paradox is reconciled to the general principles of the differential method.

M. Camus also assisted in several determinations and reports which were referred at various times to committees of the academy; and particularly in the remeasurement of M. Picard's base from Villejuif to Juvisy, which was performed by eight members, and recorded in the Memoirs for 1754.

The latter years of his life were much occupied in various engagements connected with the offices of examiner in the schools of the Royal Engineers and in that of the Artillery, to which he was nominated by the king. He undertook, for the advantage of the students in these schools, the laborious task of reducing into a uniform system a complete course of mathematical study, in which the geometrical method was as much as possible observed, and which is considered as highly creditable to his talents and exertions; it was entitled Cours des Mathématiques, 4 vols. 8vo. 14l. He also published an Elementary work on Arithmetic.

In person M. Camus was tall; his countenance was agreeable; his manners were firm, and occasionally somewhat warm; but he was far from being either morose or vindictive. He was elected a foreign member of the Royal Society of London in January 1764. He married, in 1733, Mademoiselle M. A. M. Fourrier, and had four daughters, the eldest of whom was married to M. Pagin; the others died young. His last illness was supposed to have originated from a cold taken in a professional journey during the hard winter of 1766, and to have been aggravated by affliction for the loss of his surviving daughter. He died a few months after her, on the 4th of May 1768. He left a variety of manuscripts, demonstrative of his habitual dil- gence and of the extent of his researches; but not deemed of sufficient importance to meet the hazards of posthumous publication. (Hist. Acad. Par. 1768, p. 144.) (r. v.)

Camus, Jean Pierre, bishop of Bellay, was born at Paris in 1582. He wrote a great number of pious romances adapted to the taste of his time, and other theological works. His definition of politics is remarkable—Ars non tam regendi quam fallendi homines, the art not so much of governing as of deceiving mankind. He was an exemplary prelate, and distinguished for the zeal with which he attacked the abuses of his time. He died in 1652. Moreri has given a large catalogue of his works.