Heat arises from several causes, all of which, however, manifest through the vibration of the Particles of the body evidencing the Heat. These causes may be stated as (1) Original Motion of the Particles of a body of Substance, arising from some workings of the Law of Attraction, and including Motion arising from Chemical Action, Combustion, etc. (2) From transmission or "contagion" from some other body of Substance, the Particles of which are vibrating at the rate of Heat. (3) From interrupted Motion, including friction both of the moving body with the air or other Substance, and the friction of a current of Electricity passing through the body. In each of the above cases, the _actual_ and immediate cause of the Heat is the vibration of the Particles of the Substance manifesting the Heat, although the transmitted vibratory waves, or the interrupted motion, friction, current, etc., may have been the instigator or provoker of such vibration. The interrupted motion, friction, or "wave" does not produce the Heat, but merely arouses or provokes the increased vibration of the Particles, that really manifest the Heat. At the last, remember, the Heat is in the Particles of the body that "feels" or experiences it. The vibrations of Heat seem to have the properties of causing the Molecules to draw further apart, and to manifest less Attraction, or more Repulsion, whichever way one cares to express it. This "moving away" of the Molecules tend to cause the body to increase in volume or size, and occasions what is known as "Expansion" in Substance. In this way Heat transforms Solids into Liquids; Liquids into Gases or Vapors, the change being wholly a matter of the relative distances of the Molecules. _Magnetism_ is another form of Energy, and is generally believed to be a part of the phenomena of Electricity, if indeed, not a form of Electricity itself. Science knows very little about the nature of Magnetism, but in a general way holds to the theory that it results from the vibration or motion of the Particles of Substance, as do all other forms of Energy. The magnetic qualities of a body may be increased or decreased by motion affecting the relation of the Molecules, which fact has been regarded as having some bearing on the theory.