Guillaume, a celebrated French experimental philosopher, was the son of an advocate who had left his native province of Normandy, and established himself at Paris, where the subject of this memoir was born in 1663. The exertions of genius frequently take a particular direction from accidental circumstances. A severe illness with which Amontons was afflicted in his early youth, had the effect of rendering him almost entirely deaf, and consequently of excluding him in a great measure from the ordinary commerce and amusements of society. Being compelled by this accident to depend for his enjoyments on the resources of his own mind, he began to take great pleasure in the construction of machines of various kinds, and in the study of the laws of mechanics; a path of inquiry which he pursued through life with unremitting ardour and distinguished success. One of the first objects which engaged his attention was the discovery of the perpetual motion; an attempt which, though necessarily unsuccessful, was productive of greater advantage to him than it has usually been to those who have pursued that vain chimera.

Amontons directed his views in a particular manner to the improvement of instruments employed in physical experiments; a subject which requires the finest applications of mechanical principles, and which till that time had not met with a due share of attention. In 1687, before he had attained his 24th year, he presented to the Academy of Sciences an hygrometer of his own invention, which was received with approbation by that learned body. In 1695 he published the only work which he has given to the world. It was dedicated to the academy, and entitled Remarques et Amorbach Experiences Physiques sur la Construction d'un Nouvel Clepsydra sur les Baromètres, les Thermomètres, et les Hygromètres. After Huygens' beautiful application of the pendulum to the regulation of the motion of clocks, any attempt to revive the clepsydra, an incommodious instrument, and not susceptible of much accuracy, might seem to subject its author to the imputation of not sufficiently appreciating the great importance of a discovery which has so completely changed the face of astronomical science; but the object of Amontons was to produce an instrument capable of measuring time on board ship, in circumstances where the motion of the vessel rendered such timekeepers as were then known useless. The machine which he constructed is said to have been extremely ingenious, and probably differed entirely from those of the ancients, among whom the clepsydra was in common use.

In 1689 Amontons was admitted into the Academy of Sciences, the memoirs of which he enriched with many important contributions. The first paper which he presented after his admission was one on the theory of Friction, a subject then involved in great obscurity, and on which his inquiries tended to throw considerable light. After that appeared, in succession, an account of a New Thermometer, and of numerous experiments made with the Barometer, relative to the nature and properties of Air—a detailed account of all which is given in the history of the academy. By his countrymen he is generally regarded as the inventor of the telegraph; and he had the honour of exhibiting the methods by which he proposed to accomplish the object in view, before some members of the royal family. It appears, however, from a paper read by Dr Hooke to the Royal Society in 1684, that that ingenious philosopher had brought the telegraph, in theory at least, to a state of far greater maturity than Amontons, and nearly 20 years earlier. The experiments of the latter were made about the year 1702. It may be regarded as a curious fact in the history of inventions, that although the great importance of telegraphic communication is obvious, and the method of accomplishing it was clearly explained by Hooke, and its practicability demonstrated by Amontons, it continued to be regarded as a mere jeu d'esprit, and was not regularly applied to useful purposes till nearly a century afterwards, at the time of the French Revolution. Amontons died in 1705, aged 42.