The greatest triumphs of applied science so far have been in the realm of physics and chemistry. When people think of scientific technique they think primarily of machines. It seems probable that in the near future science will achieve equal triumphs in biological and physiological directions, and will ultimately acquire as much power to change men’s minds as it already has power to deal with our inanimate environment. In the present chapter, however, I shall not be concerned with the biological applications of science, but with the more familiar and hackneyed theme of its applications in the realm of machinery.