DIFFERENT ASPECTS OF WAVES OF THE OCEAN The term " wave " is applied indiscriminately to all undulations of the surface-water, whatever their magnitude or cause. Besides the wind, earthquakes, and the attraction of the sun and moon, also produce "waves," distinguished as wind-waves, earthquake-waves, and tidal-waves, respectively. Atmospheric disturbances are, of course, the direct cause of all wind-waves ; still, the varying force of the wind, and the different angles at which it strikes the water, produces differ ent aspects of the water. Thus the slight ripple produced by a gentle breeze is called by sailors a catspaw. A con tinuous wind, rising to a heavy gale, produces a swell or billow in the open sea, converted into rollers or breakers as they near the coast. The effect of violent storms, in certain localities, is propagated for great distances in the regular heaving motion known as a ground swell, which does not cease for some time after the storm is over. Occasionally the wind, after blowing steadily for some time in a certain direction, suddenly changes.
Thus two series of waves are produced : the second crossing the first at different angles, and resulting in a peculiar trellis like appearance of the water, nautically known as a chopping sea.
So long as a wave passes over deep water, it simply rises and falls vertically—the form only advancing ; but as it approaches the shore, its lower part is checked by friction on the bottom, consequently its upper part moves faster, and is converted into a wave of translation, or an actual forward motion of the water. The confused, broken water along a shallow coast, formed by the actual advance of the waves, is called a surf The heavy surf on exposed coasts, such as on the western coasts of Africa, and the Malabar coasts of India, renders landing at all times difficult, and often dangerous. Such is the force of the water, that even "great sharks, lying in wait for their prey, are destroyed by the breakers, and are themselves overwhelmed in its fury, and dashed lifeless on the beach."—(Skertchley.)