Thus we may find much to admire and study on the sea shore at all times, but there are attractions of quite another nature that call for notice on a stormy day, especially on the wilder and more desolate western coasts. At such times we delight to watch the distant waves as they approach the shore, to see how they become gradually converted into the foaming breakers that dash against the standing rocks and wash the rattling pebbles high on the beach. The powerful effects of the sea in wearing away the cliffs are now apparent, and we can well understand that even the most obdurate of rocks must sooner or later break away beneath its mighty waves. [Illustration: FIG. 6.--BREAKERS] The extreme mobility of the sea is displayed not only by the storm waves, and by the soft ripples of the calm day, but is seen in the gentle currents that almost imperceptibly wash our shores, and more manifestly in the perpetual motions of the tides. This last-named phenomenon is one of extreme interest to the sea-side rambler, and also one of such great importance to the naturalist that we cannot do better than spend a few moments in trying to understand how the swaying of the waters of the ocean is brought about, and to see what determines the period and intensity of its pulsations, as well as some of the variations in the daily motions which are to be observed on our own shores. In doing this we shall, of course, not enter fully into the technical theories of the tides, for which the reader should refer to authoritative works on the subject, but merely endeavour to briefly explain the observed oscillations of the sea and the general laws which govern them. The most casual observer must have noticed the close connection between the movements of the ocean and the position of the moon, while those who have given closer attention to the subject will have seen that the relative heights of the tides vary regularly with the relative positions of the sun, moon, and earth. In the first place, then, we notice that the time of high tide in any given place is always the same at the same period of the cycle of the moon; that is, it is always the same at the time of new moon, full moon, &c. Hence it becomes evident that the moon is the prime mover in the formation of tides. Now, it is a fact that the sun, though about ninety-three millions of miles from the earth, has a much greater attractive influence on the earth and its oceans than the moon has, although the distance of the latter is only about a quarter of a million miles: but this is due to the vastly superior mass of the sun, which is about twenty-six million times the mass of the moon. How is it, then, that we find the tides apparently regulated by the moon rather than by the sun?