should be rightly labeled, but to stigmatize them as necessarily inferior to the natural products is, to say the least, unprogressive. We do not object to artificial indigo because the chemist has superseded the green plant in its manufacture. Why, then, should we object to a currant jelly composed of wholesome artificial products? It may not only be as good as the old-fashioned kind, but I can imagine that a connoisseur in this new venture might impart to it a flavor even more delicate than that from the kitchen. Our descendants, I am sure, will some day sit down to dinners of synthetic dishes, the products of clean laboratories, with as much appetite and pleasure as we now partake of a meal hewn from the animal and dug from the earth, and we must not object if they prefer, on esthetic grounds, the source of their food to that of ours.
But food is only one of the many things we need. We number ourselves among the very few organisms that use tools and we need energy to drive many of our tools. Historically we have abandoned in much of our work the muscle for the steam engine. Contrast the construction of a modern building by a handful of Italian workmen and a donkey engine with the wall pictures we have of the long lines of Egyptian slaves straining every muscle as they pull a heavy load at the end of a rope.
But have we done best to ignore the muscle? When this organ is functioning at its highest, it yields two kinds of energy, heat and power to do mechanical work about in the proportion of two thirds heat to one third work. From the energy that enters the ordinary steam engine about one tenth is given back in work and the other nine tenths are dissipated as heat. Even in the highest grade of turbine engines, this efficiency seldom reaches as much as a quarter of the available energy. Thus the muscle returns us over thirty per cent, of its energy in effective work, and the best steam engines only about twenty-five per cent. If we knew the secret of muscle action, I have no doubt that a mechanism could be constructed that would far outrun the steam engine as a means of doing work.
Another kind of energy that we seek is light. Primitive man was forced to content himself with the sun by day and the moon and stars by night. When he first struck fire, artificial light came as well as warmth, and from that day to this we have witnessed a long succession of improvements in the production of artificial light. But in none of these has man rid himself of the association of heat with light. Every device for illumination that has been put forward yields more heat than light. Our ordinary gas flame yields between one and two per cent, of light and the remaining ninety-eight or -nine per cent, is lost in heat. No wonder that the modern gas corporation is advertising itself as a convenient source of heat and power. Many of us who serve it as consumers have come to regard this by-product as the most impor-
