The motion of the individual atom as heat may be, and is, as rapid as light itself when the temperature is sufficiently high, but it does not travel along a conductor rapidly as the electro-atomic motion will. If we apply heat to the end of a metal rod it will travel slowly along the rod. But if we make the rod a conductor of electricity it travels from atom to atom with a speed nearer that of the light ray through the ether. Some modern writers have attempted to explain all the phenomena of electricity as having their origin in a certain play of forces upon the ether, and there is no doubt but that the ether plays an important part in all electrical phenomena as a medium through which energy is transferred; but ether-waves that are set in motion by the electrical excitation of ordinary matter are no more electricity than the ether-waves set up by the sun in the cold regions of space are heat. They become heat only when they strike matter. Heat, _as such_, begins and ends in matter;--so (I believe) does electricity. Do not be discouraged with these feeble attempts to explain the theory of electricity. All I even hope to do is to establish in your minds this fundamental thought, to wit, that there is really but one Energy, and that it is always expressed by some form of motion or the ability to create motion. Motions differ, and hence are called by different names. If I should set an emery-wheel to revolving and hold a piece of steel against it the piece of steel would become heated and incandescent particles would fly off, making a brilliant display of fireworks. The heat that has been developed is the measure of the mechanical energy that I have used against the emery-wheel. Now, let us substitute for the emery-wheel another wheel of the same size made of vulcanized rubber, glass or resin. I set it to revolving at the same speed, and instead of the piece of steel, I now hold a silk handkerchief or a catskin against the wheel with the same force that I did the steel. If now I provide a Leyden jar and some points to gather up the electricity that will be produced (instead of the heat generated in the other case), it would be found that the energy developed in the one case would exactly balance that of the other, if it were all gathered up and put into work. The electricity stored in the jar is in a state of strain, like a bent bow, and will recoil, when it has a chance, with a power commensurate with the time it has been storing and the amount of energy used in pressing against the wheel.