The tides are produced by two pairs of great waves which travel round the earth each day—a greater pair caused by the attraction of the moon, a lesser pair caused by the sun. The moon, by reason of its nearness to the earth, produces by far the greater influence, but the tides are also subject to all kinds of local influences. The eastern coast of Asia and western side of Europe are exposed to extremely high tides; while in the South Sea Islands they scarcely reach the height of twenty inches. There is hardly any tide in the Mediterranean, separated as it is from the ocean by a narrow strait. “The highest tide which is known occurs in the Bay of Fundy, which opens up to the south of the isthmus uniting Nova Scotia and New Brunswick. There the tide reaches forty, fifty, and even sixty feet, while it only attains the height of seven or eight in the bay to the north of the same isthmus. It is related that a ship was cast ashore upon a rock during the night so high, that at daybreak the crew found themselves and their ship suspended in mid‐air, far above the water.” The winds have an immense influence on the height of tides, and also on the waves. The highest known waves are found off the Cape of Good Hope (p. 89) at the period of high tide, under the influence of a strong north‐west wind which has traversed the Atlantic, pressing its waters round the Cape. “The billows there,” says Maury, “lift themselves up in long ridges, with deep hollows between them. They run high and fast, tossing their white caps aloft in the air, looking like the green hills of a rolling prairie capped with snow, and chasing each other in sport. Still, their march is stately and their roll majestic. Many an Australian‐bound trader, after doubling the Cape, finds herself followed for weeks at a time by these magnificent rolling swells, furiously driven and lashed by the ‘brave west winds.’ These billows are said to attain the height of thirty, and even forty feet; but no very exact measurement of the height of waves is recorded.” Those off Cape Horn are rather less in height. _Spray_ is dashed over the Eddystone Light, 130 feet high. After a great storm in Barbadoes in 1780, some old and heavy cannons were found on the shore, which had been thrown up from the bottom of the sea. If waves in their reflux meet with obstacles, whirlpools result, such as those in the Straits of Messina, between the rocks of Charybdis and Scylla made famous by Homer, Ovid, and Virgil, and once much dreaded, but now little feared.