WILLIAM H. HOBBS. The River System of Connecticut, Jour. Geol., vol. 9, 1901, pp. 469-485, pl. 1; Lineaments of the Atlantic Border Region, Bull. Geol. Soc. Am., vol. 15, 1904, pp. 483-506, pls. 45-47; The Correlation of Fracture Systems and the Evidences for Planetary Dislocations within the Earth’s Crust, Trans. Wis. Acad. Sci., etc., vol. 15, 1905, pp. 15-29; Repeating Patterns in the Relief and in the Structure of the Land, Bull. Geol. Soc. Am., vol. 22, 1911, pp. 123-176, pls. 7-13. CHAPTER XVIII THE FORMS CARVED AND MOLDED BY WAVES =The motion of a water wave.=—The motions within a wave upon the surface of a body of water may be thought of in two different ways. First of all, there is the motion of each particle of water within an orbit of its own; and there is, further, the forward motion of propagation of the wave considered as a whole. [Illustration: FIG. 247.—Diagram to show the nature of the motions within a free water wave.] The water particle in a wave has a continued motion round and round its orbit like that of a horse circling a race course, only that here the track is in a vertical plane, directed along the line of propagation of the wave (Fig. 247). Each particle of water, through its friction upon neighboring particles, is able to transmit its motion both along the surface and downward into the water below. The force which starts the water in motion and develops the wave, is the friction of wind blowing over the water surface, and the size of the orbit of the water particle at any point is proportional to the wind’s force and to the stretch of water over which it has blown. The wind’s effect is, therefore, cumulative—the wave is proportional to the wind’s effect upon all water particles in its rear, added to the local wind friction. The size or _height_ of the wave is measured by the diameter of the orbit of motion of the surface particle, and this is the difference in height between trough and crest. The distance from crest to crest, or from trough to trough, is called the _wave length_. Though the wave motion is transmitted downward into the water there is a continued loss of energy which is here not compensated by added wind friction, and so the orbital motion grows smaller and smaller, until at the depth of about a wave length it has completely died out. This level of no motion is called the _wave base_. In quiet weather the level of no motion is practically at the water’s surface, and inasmuch as the geological work of waves is in large part accomplished during the great storms, the term “wave base” refers to the lowest level of wave motion at the time of the heaviest storms. Upon the ocean the highest waves that have been measured have an amplitude of about fifty feet and a wave length of about six hundred feet.