Guillaume Amontons (31.08.1663 - 11.10.1705) was a French physicist and a member of the Paris Academy of Sciences (1699). Born in Paris. He studied physics, mathematics, applied and celestial mechanics and architecture on his own. He was almost completely deaf.
His work was in the field of mechanics, thermometry and molecular physics. He made observations on gases and worked on improving physical instruments, chiefly hygrometers, barometers and thermometers. He constructed a hygrometer (1687), a mercury-free barometer (1695), an air thermometer and (1702) a barometer with a U-shaped tube for use on ships. In 1702 he established a fixed thermometric point — the boiling point of water, found the direct proportionality between the temperature and the pressure of a gas, and established the relation between the density of air and its pressure. He measured the expansion of air on heating. Using the barometer as an altimeter, he attempted to test the validity of the Boyle — Mariotte law at low pressures. He proposed a method of graduating the spirit thermometer. He implied (1703) the existence of an absolute zero of temperature. He studied friction and discovered (1699) the laws of external friction of solids. He improved (1703) the pyrometer.