The first thermometer scale to give satisfaction was devised in 1714 by
Fahrenheit. He determined the fixed points on the thermometer in a very
novel manner. Having been born at Dantzig, he took for the zero point on
his scale the lowest temperature observed by him at Dantzig, which he
found was that produced by mixing equal quantities of snow and
sal-ammoniac. The space between this point and that to which the mercury
rose at the temperature of boiling water he divided into 212 parts. He
determined, with his thermometer, that the atmospheric pressure governed
the boiling point of water. Today the Fahrenheit thermometer is used
extensively, and has for its freezing point 32° and for its boiling
point 212°.
Another scale that has not become too well known, because of the fact
that it did not meet with public favor, was devised by a Frenchman,
named Reaumur, in 1730, and bears his name. He determined the freezing
point of the scale at 0° and the boiling point of water at 80°.
Another Frenchman, named Anders Celsius, devised a scale with the
boiling point of water at 0° and the freezing point at 100°. In 1743 a
Frenchman, named Christin, living at Lyons, France, reversed the points,
and today the scale is known as the Centigrade scale, and, together with
the Fahrenheit scale, is used almost exclusively wherever thermometers
are required.