_The breakers of the ocean--Caverns and fairy bridges of Kilkee--Italy and Sicily--The Shetland Islands--East and south coast of Britain--Tracts of land swallowed up by the sea--Island of Heligoland--Northstrand--Tides and currents--South Atlantic current--Equatorial current--The Gulf Stream--Its course described--Examples of its power as an agent of transport._ While the rain, the rivers, and the streams, are thus wasting away the mountains and plains of the interior country, the waves of the sea are exerting a power no less destructive on the coasts of islands and of continents. The breakers dashing against the foot of a lofty cliff, dissolve and decompose and wear away the lower strata; and the overhanging rocks, thus undermined, fall down in course of time by their own weight. With the next returning wave these rocks are themselves hurled back against the cliff; and so, as some one has happily remarked, the land would seem to supply a powerful artillery for its own destruction. The effects of the breakers are often very unequal, even on the same line of cliffs. Some parts of the rock are more yielding than others, or perhaps they are more exposed to the action of the waves, or perhaps they are divided by larger joints and more freely admit the destructive element. These parts will be the first to give way, while the harder and less exposed rock will be left standing: and in this way forms the most capricious and fantastic are produced. No finer examples could be wished for than those which are seen in the neighborhood of Kilkee, and along the promontory of Loop Head, in the county of Clare. Sometimes the ground is undermined with caverns, into which, when the tide is coming in, the waves of the Atlantic rush with resistless force, making new additions each day to the accumulated ruins of ages. Sometimes lofty pinnacles of rock are left standing in the midst of the waters, like giant sentinels stationed there by Nature to guard the coast. In one or two instances these isolated fragments are connected with the main land by natural arches of rock, which are called _fairy bridges_ by the people; but more commonly they appear as rocky islets, and answer exactly to the poet’s description-- “The roaring tides The passage broke that land from land divides; And where the lands retired the rushing ocean rides.” It is interesting to observe in passing, that, in the original verses of the Æneid, of which these lines are Dryden’s translation, Virgil has recorded a belief which prevailed in his time, and which, upon scientific grounds, is now regarded as highly probable by Geologists, that the island of Sicily had been once connected by land with Italy, and was separated from it by the action of the waves: