Only ideal machines convert one form of energy exclusively into one other, desired, form. A plant is a machine that uses the rays of the sun directly for building up its body, a thing man can not do; but it is not a perfect machine, since it does not convert all the solar energy it receives to its own uses. From the human standpoint, a plant is a machine for storing up energy of solar radiation in the form of food for man. We have the data for comparing the energy available to the plant with that stored up. The result of the comparison is striking. The plant stores up, in fact, less than one-hundredth part of the energy it receives. The relation between the total energy received by a machine and that which it utilizes we call the figure of merit of the machine. This technical expression is but an extension of a colloquial figure of speech: thus, we call an electric generator "good" if it converts 97 per cent, of energy received into electric current, and "bad" if it only converts 85 per cent. In the final summing up, the moral concept of "good" and "bad" must unavoidably rest on the same basis, inasmuch as all things that happen are but energy manifestations.
Every change in the form of energy is accompanied by a dissipation of part of it in the form of heat. This loss may be compared with the material losses, in the way of saw-dust, chips, etc., which accompany the work of carpenter or stone cutter. We may look on the heat dissipated by machines as an undesirable by-product. Actual machines fall far short of ideal ones in their figure of merit, that is in their efficiency, but those made by human hands are relatively much less wasteful of energy than those furnished by nature.
The inefficiency of our practical mechanisms, compared with their theoretical efficiency, is a measure of our stupidity or unskillfulness. In this respect improvement is constantly taking place. All technology is devoted to the conversion of crude energy into forms useful to man. The "figure of merit" in the transformation is a gauge of our culture in this field. Let us consider what is the scope, upward, of technology in the sense referred to. We have not yet quite got rid of the ancient view of work, and hence of technical operations, as being something low. It is interesting to recall that Aristotle held the institution of slavery, on which the civilization of Greece and Rome rested, to be inevitably necessary for all time, since he could not picture to himself how the crude labor of grinding corn, pumping water and the like could be done at all, if not by slaves. Later times have taught us to solve the slave problem by the inanimate agencies of wind, water and coal, which make superfluous the lowest forms of human labor. In this illustration we see to what a high degree technical progress has had a humanizing influence by reducing the amount of de-humanizing work. Without technical advances, we would have to have slaves to-day, and would still be, in the development of social conscience, ages behind
