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Quantitative measurements in temperature, based upon the calorie, have a definite place in physics; and those based on the British thermal unit have a broad application in various economies. Human sensitiveness to heat does not pertain to quantity but to intensity. A large block of ice at 30° may contain more heat, quantitatively considered, than a red-hot horseshoe. If carried into a room whose air was far below freezing, the ice might warm the room to a greater degree than would the horse-shoe. Humanity, and indeed, all living things require the intensity of heat that enables living organisms to function naturally and properly. The vital questions therefore are—“How warm is it?”—or, “How cold is it?”—or, “Is physical comfort satisfied?” These conditions depend upon intensity of heat—that is, upon temperature.

Temperature.—The term temperature has a broad application. It is an expression of the varying warmth of earth, air and water, with relation to life.

The unit of temperature is a degree, a measured part of the expansion which a column of mercury within a tube undergoes when heated from the melting point of ice to the boiling point of water at sea level.