ON THE _Various Forces of Nature_ AND THEIR RELATIONS TO EACH OTHER: _A COURSE OF LECTURES DELIVERED BEFORE A JUVENILE AUDIENCE AT THE ROYAL INSTITUTION_ BY MICHAEL FARADAY, D.C.L., F.R.S. EDITED BY WILLIAM CROOKES, F.C.S. [Illustration: Colophon] _A NEW EDITION, WITH ILLUSTRATIONS._ London: CHATTO & WINDUS, PICCADILLY. 1894. PREFACE. Which was first, Matter or Force? If we think on this question, we shall find that we are unable to conceive of matter without force, or of force without matter. When God created the elements of which the earth is composed, He created certain wondrous forces, which are set free, and become evident when matter acts on matter. All these forces, with many differences, have much in common, and if one is set free, it will immediately endeavour to free its companions. Thus, heat will enable us to eliminate light, electricity, magnetism, and chemical action; chemical action will educe light, electricity, and heat. In this way we find that all the forces in nature tend to form mutually dependent systems; and as the motion of one star affects another, so force in action liberates and renders evident forces previously tranquil. We say tranquil, and yet the word is almost without meaning in the Cosmos.--Where do we find tranquillity? The sea, the seat of animal, vegetable, and mineral changes, is at war with the earth, and the air lends itself to the strife. The globe, the scene of perpetual intestine change, is, as a mass, acting on, and acted on, by the other planets of our system, and the very system itself is changing its place in space, under the influence of a known force springing from an unknown centre.