(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 secluding 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. His attempts, though necessarily unsuccessful, were productive of greater advantage to him than they have usually been to those who have pursued that vain chimera; for in the course of his reflections on the subject he became convinced, that, in order to make any progress in mechanics, it is necessary to be acquainted with certain principles, the knowledge of which can only be acquired through the medium of geometry. He therefore assiduously applied himself to the study of this latter science, and his progress in it prepared the way for his future mechanical discoveries. He is said to have derived so much pleasure from the uninterrupted pursuit of these interesting speculations, that he refused to employ any remedy for his deafness, lest he should be diverted from them by an increased facility of intercourse with the world; resembling in this respect, says Fontenelle, the ancient sage who put out his eyes that he might enjoy his philosophic meditations without distraction.

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 Experiences Physiques sur la Construction d'un nouvel Clopsydre, sur les Barometres, les Thermometres, et les Hygrometres. After Huygens' beautiful application of the pendulum to the regulation of the motion of clocks, any attempt to revive the clepsydra, an uncommonly 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 1669 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.

Although most of the instruments invented by Amontons have been superseded by others more accurate and convenient, yet they contributed to give a greater precision than had been attained before his time, to experiments and physical investigations, and consequently to accelerate the progress of experimental philosophy, which from that period began to make rapid advances. He possessed a singular talent for contriving and conducting experiments, and showed great address in obviating or eluding the difficulties which, even in the hands of the most skilful and Amoreans expert, so frequently occur to prevent their success. His industry and activity promised still more important services to science, when, to the great regret of his contemporaries, he was suddenly cut off by inflammation, at the age of 42 years. His manners are represented to have been simple and unostentatious, his character candid and frank, entirely free from affectation or pretension of any sort; and he lived in comparative obscurity, because, as his eulogist ingeniously observes, he was unequainted with the arts of the courtier, and knew no other means of acquiring reputation or fortune, than those of real merit and useful services to mankind. See his Eloge by Fontenelle. (s.)

AMORÆANS, a sect or order of Gemaric doctors, or commentators on the Jerusalem Talmud. The Amoreans succeeded the Mischnic doctors. They subsisted 250 years, and were succeeded by the Sebureans.