WAVES NATURE OF MOTION OF THE OCEAN It must be distinctly borne in mind that the motion imparted to the water by the impact of the wind at various angles is not progressive, although apparently so. The form of the wave moves, but not the water, that is, the same wave as it advances is not composed of the same water. The nature of wave-motion is very clearly shown by a common illustra tion. For instance, when a long carpet is shaken, waves or undulations are produced, which travel successively from one end to the other. Both ends are stationary, and no one would think for a moment that a single thread has—relatively to the other threads—changed its place. That a fixity of relative position may be preserved, and yet a wave-like motion be propagated is, perhaps, still more clearly shown when a breeze passes over a corn field. The same wave like motion is produced, but not a stalk has permanently changed its normal position. The fixity of the component threads of the carpet, and the attachment of the stalks of corn to their roots, are, of course, stronger than the actual cohesion between the particles of water ; yet the motion is almost precisely the same—that is, the motion of the wave is not attended by an actual permanent change in the position of its component particles. The " form " of the wave moves for
ward without any corresponding advance of the water ; a wave being, in fact, simply a vertical or up-and-down motion of the particles of the water, which resume their original positions when the disturbing influence is withdrawn. That the motion is simply propagated along the surface, like the "waving" of a corn field, may be easily proved by throwing a cork on the water when slightly agitated by the wind. If the water actually advanced, the cork would certainly be carried along with it, instead of which it simply oscillates up and down ; and if its bearings relatively to any fixed object on shore be ac curately observed, it will be seen to retain the same position.