W. D. Miller

“ Since all forms of energy are essentially kinetic or potential, or the energy of heat-motion, it is sufficient if we examine the laws with regard to these.
A body is said to possess potential energy when in virtue of its position it can do work. A raised weight possesses potential energy, which, by a simple contrivance, may be converted into work; a bent bow and a wound-up spring possess energy of position, because of the separation of their molecules, which we may avail ourselves of by allowing them to fall back into their natural positions. ”

“ Let us consider a hot spherical body, whose energy we wish to communicate to another equal sphere, absolutely cold, and suppose for a moment that they have a thin outside crust absolutely impermeable to heat, and that the mass of each sphere is concentrated in a single little ball, to whose motion the heat is due, the ball in the cold sphere will of course lie still at the bottom, while the other is flying about at an inconceivable rate ”

“ Long after the earth has become uninhabitable, it may be, the kinetic energy of every planet of our system being frittered away into heat by friction on the ethereal medium, they shall find their way, one by one, into the sun's mass, thus giving him the energy by which he will work on for long ages after they are defunct ”

“ The energy so spent was long a puzzle to scientific minds, and was believed to be absolutely destroyed, until the experiments of Rumford and Davy fully demonstrated that the work spent in overcoming friction was transformed into heat—a form of kinetic energy, it is true, but of such an inferior class as to have entirely escaped the notice of the shrewdest observers. It is, in general, a very easy matter to transform the whole of the potential or kinetic energy of a body into heat ”

“ In this instance energy of position is at first transformed into energy of motion, but the moment the mass strikes the ground all motion, as far as we are able to discover, is gone; but we know that the motion of the mass as a whole has only been transformed into motion of the particles among each other, and of the particles of the body on which the mass impinges, constituting the phenomenon of matter commonly called heat. ”

“ The first two states are available as sources of mechanical energy, but in the third state the energy is scattered into an infinite number of infinitely small energies, as it were, and, in the case of small masses at least, is lost forever as far as doing work is concerned; and so much energy is let down from a high to a low class, and the whole energy of the universe is rendered less available by a corresponding amount. ”

“ A boxer may receive a blow from his antagonist which may stagger him, and perhaps throw him off his balance, but yet do him no permanent injury; while a rifle-ball with half the energy, though it might not disturb his equilibrium, would in all probability inflict instant death. Any number of examples of this kind might be given to show to what an extent the form which a given amount of energy assumes and the constancy of its effects are dependent upon the matter with which it is associated. ”

“ The first three are wholly due to the sun, and the fourth in part, so that by far the greater amount of our available energy is derived from the sun. "For it is he who separates the carbon from the oxygen of the carbonic acid and enables them to combine again, whether in the furnace of the steam-engine or in the animal body." It is he who sets the air in motion, and raises up the water whose fall is to turn the wheels of our mills. We are thus receiving a constant supply of energy from the sun, and his must be diminished in a corresponding degree. ”

“ That a reversible engine is the most perfect engine possible. And, consequently, if we possessed a reversible engine, and a condenser absolutely deprived of heat, we could convert the whole of the heat from the boiler into mechanical energy. But since it is impossible to obtain an absolutely cold condenser, there is always a large fraction lost in attempting to convert heat into mechanical energy. ”

“ It thus becomes a question of primary importance as to how energy is connected with and dependent upon matter, and as to how its form and availability are influenced by its connections.
That the same amounts of different kinds of energy, or even of different forms of the same kind, are vastly different in their effects, is a thing of every-day experience. A mass raised above the earth's surface possesses in consequence a certain amount of energy, in virtue of which it can do work ”

“ But as a reversible process is the only one which can maintain itself for all time, it follows that our earth is gradually lowering its energy from high to lower classes; the ultimate form to which all must be reduced being that which has its source not in the position or motion of masses, but of molecules. ”

“ IT follows, as a direct consequence of the most usual definition of matter as "the vehicle of energy," and is also arrived at from experience, that energy never does and never can manifest itself except in connection with matter. And, although we could readily conceive of, and in fact see many instances of, matter without energy, yet no person of sound intelligence, or, as said Newton, "no one with a competent faculty of thinking," could for a moment entertain the idea of energy without matter ”

“ If a body be allowed to fall, it necessarily loses the energy which it had in virtue of its position as it approaches the ground, but at the same rate it gains a different kind proportional in amount to the space passed through, and consequently to the square of the velocity. ”

“ But, practically, we are unable to realize such a law, because of the resistances we meet with in friction, electric induction, etc., so that any series of actions taking place in nature is not a reversible one, or the mechanical energy spent can never be wholly restored to its primitive condition. ”

“ If, now, the number of balls becomes infinite, or if we reduce our imaginary spheres to two real spheres, and substitute molecules for balls, then 1: is not an exaggeration of the chance of all the energy being in one of the spheres at any time in the future ”