# Page:Popular Science Monthly Volume 18.djvu/383

5. The boiling-point of water at the level of the sea, and with a barometric pressure of 760 mm. ${\displaystyle =}$ 29∙922 inches in the latitude of 45°, is the second point in the thermometer scale to be fixed. To do this the thermometer is exposed to the steam of pure water, and, from the observed height of the barometer, the known elevation and latitude of the place of observation, the true boiling-point is computed from the observed one, and the 100° C. or 212° F. is thus fixed.