THERMOMETER

is graded by being placed first in snow and then in the steam of boiling water. In each case a mark is made opposite the end of the column of mercury, and the one mark denote; freezing-point, while the other denotes boiling-point. The space between is then divided into a number of equal parts, which vary according to the description of thermometer. In a Fahrenheit T. the number is x8o and as the freezing-point is 320 the boiling point; becomes 2120 In the Centigrade,, which is used for scientific purposes,. freezing-point is marked 0°, and boiling-point ioo°.