"It is an interesting question to ask if Tyndall were living today, and if a publisher should ask him to bring his book up to date, what title would he give to it? He certainly would not retain the title Heat as a Mode of Motion nor would he, in view of the all-embracing nature of electricity, term it Electricity, a Mode of Motion. The extension of our views of energy would require for its popularization all his power as an eloquent expounder. We have made an astonishing advance since his time: the subject of physics has broken away from comparatively narrow limits and has made even chemistry and biology a part of it. The physicist has discovered that all the life of the world depends upon s of energy which come from the sun."
John Trowbridge was an American physicist, noted for his research into electricity and magnetism, and for his innovations in scientific education.
"In the tradition of Joule, Helmholtz, and their followers, Trowbridge argued that because electrical and magnetic energy were convertible into , and heat had its equivalent in , then electricity and magnetism were reducible to the purely mechanical properties of underlying atoms."
"In order to make measurements of force, it is essential that the should be uniform—that is, the should be straight, and the pull or push along them should be the same at any point in the field. If the lines of force are not straight, a pendulum in swinging across these curved lines of force would not be uniformly acted upon by equal parallel forces. It would move under the influence of one force in one direction, and at another time under the influence of another in a different direction. There could be no uniformity in its motion in different parts of such a curved field of force. In all our experiments, therefore, we endeavor to make our measurements in fields of uniform force, whether these fields be s, ."