it the way it is to go. It bends the great ocean-stream into an enormous eddy or whirlpool, which is for ever circling round and round. The heavy salt water advances towards the pole along one side of the ocean basin, and the light, fresher water advances from the poles towards the tropics, along the other side of the basin; and the stream crosses eastwards, by overshooting the earth towards the poles, and it crosses westwards by allowing the earth to overshoot and pass by it within the tropics and near to the equator. There is thus a vast ocean-whirlpool, circling round and round, on each side of the equator, both in the Great Ocean and in the Atlantic. But, in consequence of the peculiar circumstances in which it is placed, the ocean-whirlpool of the North Atlantic is more marked than the others; it is also more interesting and better known, because it extends its influences to the British Isles.

When the westward current of the Mid-Atlantic has traversed the basin of this ocean, it passes to the north of Cape St. Roque, and encounters the northern coast of South America, which here crosses the equator obliquely, facing towards the north-east. Having been turned somewhat northwards by the general slope of the coast, it flows along several hundred miles, until at length it passes between the island of St. Domingo and the South American shore, and so enters the Caribbean Sea. From the Caribbean Sea, it sweeps past the Promontory of Yucatan, and is caught in the Gulf of Mexico, which is formed like a great reaping-hook, and moves along, in consequence of the earth's rotation, in the opposite direction-that is, towards the east.

Having been thus embayed in the Gulf of Mexico, this current escapes to the north of the island of Cuba, rushing forth like a mighty salt-water-river 120 miles wide and 3000 feet deep, and moving with the speed of four miles and a half in the hour. This ocean-river here has a volume one thousand times as large as the mightiest of river-streams, the great Amazon. Before

anything was known concerning the true nature or cause of this remarkable ocean-stream, its deep blue current was observed pouring forth from the Gulf of Mexico, and this gulf was very naturally conceived to be, in some mysterious way, the source of the flow. The current hence received the name of "The Gulfstream," which it still retains. The Gulf-stream is, however, nothing but a part of the great oceanic whirl

pool of the North Atlantic, where it is condensed, and made more striking and obvious as a current by the form of the land which it is compelled to pass.

The Gulf-stream having issued from the Gulf of Mexico, between Florida and Cuba, proceeds along the American coast nearly as far as Newfoundland; it then bends to the east and crosses the ocean, passing the Western Isles, and falling with diminished force even on the shores of Ireland. From the Western Isles it turns towards the south, flowing past the Cape de Verde

Islands, and then again directing its course to the American shore. The stream, with a breadth varying in different places from 50 to 250 miles, thus performs a circular voyage of about 3800 miles.

Towards the end of the fifteenth century, an Italian navigator, Christopher Columbus, sailed from Spain with three small ships, bent upon a very bold and novel expedition. He had frequently before been at the Canary Isles, and had stood gazing from their shores out upon the wide sea to the west. Occasionally, while doing this, and while reflecting upon the figure of the earth, he had observed that fragments of drift-wood, the seeds of plants, and other productions of land, were thrown upon the coast, as if brought from some distant country, lying far out of sight in that direction. After long pondering on these things, and weighing many suggestions that came in connection with them, the conviction was at last forced upon his mind that the place from which they came must be the eastern land of India, and that it would be possible to get to India by sailing over this western sea. Having, after much per severance and labour, brought first a rich Spaniard, Alonzo Pinzon by name, and then the King of Spain himself, to think favourably of his views, a little fleet was fitted out under his command, and made over to his guidance. Columbus went first to the Canary Isles, and then started off boldly to the west, pushing forward into the open and hitherto untraversed ocean, in the certainty that, if he persevered long enough, he must at length find a shore on its further side. After a voyage of five weeks he found, not the expected land, but first the West India Islands, and afterwards the New World -the great American Continent. While, however, he was sailing westward towards these places, and was yet only a few days from the Canaries, he saw ahead of his vessels what he believed to be a part of the land he was looking for. It had the appearance of being a broad green meadow. But when the ships were brought cau

tiously up to this imagined land, it proved to be nothing but a closely packed mass of floating seaweed. Day after day Columbus pushed on through the entanglement of these weeds without coming to any end of the troublesome impediment. The "Ocean Meadow" seemed to be without a bound. The clear and unencumbered sea was not again reached until the vessels were within three or four hundred miles of the outlying islands of the west. It has since been ascertained that there is a large space in the middle of the North Atlantic, seven times as large as France, which is almost choked up by these weeds. This space is now called "The Sargasso Sea," the word Sargasso being the name by which the Spaniards originally designated this entangling and floating weed. This Sargasso sea is a true ocean-meadow. Countless numbers of living creatures, shell-fish, crabs, rayed-animals, and true fishes pasture upon it, and may commonly be seen playing about amidst its leaves.

The question then here occurs, as it did to Columbus and his companions, How is this Ocean-meadow formed? Why is this large quantity of floating sea-weed always gathered together in this precise spot of the ocean? If the form and position of the Sargasso sea be drawn upɔn paper, and the situation of the great circular whirlpool of the North Atlantic, already described, be also laid down on the same paper, the meaning of its presence becomes plain enough. The circular stream surrounds the Sargasso sea like a border. The Sargasso sea is the centre of the great Ocean-whirlpool. It is the middle of the eddy into which all floating substances are drawn. If small fragments of cork or wood, and bits of straw, be scattered over the surface of a basin of water, and the water in the basin be then made to whirl rapidly round, the floating fragments will all be seen to collect in the middle of the basin, where the force of the whirling motion has the least effect. The moving water pushes the fragments in out of its way, by the friction it exerts,

as its particles rush past them. As the water in the Atlantic basin is in rapid whirling motion, floating bodies are driven in to the centre of the whirl in the same way, and hence the Ocean-meadow of green, tangled gulf-weed in the midst of the gulf-stream eddy,

In the above figure the position of the North Atlantic eddy, and of the Sargasso sea, is represented to the eye. Columbus and his companions, on their first voyage across the Atlantic, sailed from the Canary Isles to San Salvador, in the Bahama group. Consequently they passed directly through the centre of the great Oceanwhirlpool, as will be seen by reference to the sketch given above.