Measurement of Heat.

In the case of pain, etc., the only name we have for this sensation is "the sensation of heat."

When we require an adjective to denote that a phenomenon is related to heat, we shall call it a thermal phenomenon. For instance, we shall speak of the thermal conductivity The measure of a material's ability to allow heat to pass through it. of a substance or of thermal radiation to distinguish the conduction and radiation of heat from the conduction of electricity or the radiation of light. The science of heat has been called (by Dr. Whewell William Whewell (1794–1866), an influential English scientist and philosopher who coined terms like "scientist" and "physicist." and others) Thermotics, and the theory of heat as a form of energy is called Thermodynamics. In the same way, the theory of the equilibrium of heat might be called Thermostatics, and that of the motion of heat Thermokinematics.

The instrument by which the temperature of bodies is registered is called a Thermometer, or measurer of warmth, and the method of constructing and using thermometers may be called Thermometry.

The instrument by which quantities of heat are measured is called a Calorimeter, probably because it was invented at a time when heat was called Caloric An obsolete scientific theory that heat was a self-repellent fluid.. The name, however, is now well established and is a convenient one, as its form is sufficiently distinct from that of the word Thermometer. The method of measuring heat may be called Calorimetry.

A certain quantity of heat, with which all other quantities are compared, is called a Thermal Unit. This is the quantity of heat required to produce a particular effect, such as to melt a pound of ice, or to raise a pound of water from one defined temperature to another defined temperature. A particular thermal unit has been called by some authors a Calorie.

We have now obtained two of the fundamental ideas of the science of heat: the idea of temperature, or the property of a body considered with reference to its power of heating other bodies; and the idea of heat as a measurable quantity, which may be transferred from hotter bodies to colder ones. We shall consider the further development of these ideas in the chapters on Thermometry and Calorimetry.