MAYER (Tostas), in biography, a very able German astronomer and me chanic in the eighteenth century, was born at Marspach, in the duchy of Wit. temberg, in the year 1723. His father was an ingenious civil-engineer, who particu larly excelled in hydraulics ; and young Tobias, who was fund of observing him while at work, displayed an early inqui sitiveness concerning such ingenious pur suits, and from the age of four yearsbe gan to design machines with the greatest dexterity and justness. The death of his father, however, whom he lost when very young, probably prevented him from be ing educated to that employment. Pos sessing but scanty means for obtaining as sistance in his studies, he was obliged to rely on his own energies, by which he made himself a proficient in mathematical learning, and „became qualified to be an able instructor of others. While thus oc cupied, he also assiduously cultivated an acquaintance with classical and polite literature, and learned to write the Latin tongue with elegance. So well establish ed was his reputation when he had at tained to his eight-and-twentieth year, that the university of Gottingen nominat ed him to the chair of mathematical pro fessor ; and not long afterwards he was admitted a member of the Royal Society in that town. From this time, every year of his short, but glorious life, was distin guished by some considerable discove. ries in geometry or astronomy. He in vented several useful instruments for the more commodious and exact measure ment of angles on a plane. He corrected many errors in practical geometry, trac ing them to their origin, in the refrac tions occasioned by terrestrial objects. Afterwards he particularly applied him study the theory of the moon, ifs appearances, the question of its atmo sphere, and the reciprocal actions of the sun, earth, and moon, upon each other.
He then extended his observations to the planet Mars, and the fixed stars ; deter mining with greater exactness than before the places of the latter, and ascertaining that, though commonly denominated fix ed, they possess a certain degree of mo tion relative to their respective systems. Towards the end of his life the magnetic needle engaged his attention, to which lid assigned more certain laws than those be fore received. To these various inquiries and observations he applied with such in defatigable assiduity, that he died, ex hausted and worn out by his labours, in 1762, when only 39 years of age. His ta ble of refractions, deduced from his as tronomical observations, agrees very nice ly with that of Dr. Bradley; and his theory of the moon, and astronomical tables and precepts, were so well received, that they were rewarded by the English Board of Longitude with the premium of 3,000/. which sum was paid to his widow after his decease. These tables and precepts were published by the board in the year 1770. The principal works which he gave himself to the public were, "A New and General Method of resolving all Geome trical Problems, by means of Geometri cal Lines," 1741, 8vo. in German. " A 'Mathematical Atlas, in which all the Ma. thematical Sciences are comprised in six ty Tables," 1748, folio, in German. " A Description of a Lunar Globe, construct ed by the Cosmographical Society of Nu remberg, from new Observations," 1750, 4to. also in German. Several exact Maps ;" and some valuable papers in the Memoirs of the Royal Society of Gottingen. The first volume of his works was published at that place in 1775, in folio.