18. Currents of the Atlantic Ocean.-The South Atlantic Current is a continuation of L'Agullas Current. It flows northerly along the African coast to the parallel of St. Helena, whence its course is more easterly till it is turned to the westward by the form of the coast, and the opposition of the Guinea Current from the north; it then changes into

The Equatorial Current of the Atlantic.-This stretches across the ocean on both sides of the equator till it reaches the central point between Africa and South America: it then divides into two portions, one of which flows along the coast of Brazil, and passes with considerable rapidity round Cape Horn, through the Straits of Magellan into the Pacific. The other branch turns northward and flows through the Caribbean Sea into the Gulf of Mexico. In passing along the coast of Guiana, a portion of it, between the islands of Trinidad and Martinique, receives the name of the Guiana Current, and its continuation to the peninsula of Yucatan is called the Caribbean Current, then under the name of the Gulf of Mexico Current it makes a complete tour of the Mexican Gulf.

19. The Gulf Stream. This celebrated stream issues from the Gulf of Mexico with a velocity of 4 or 5 miles an hour, and flows to the north-east, along the coast of the United States. As it proceeds northwards, it recedes gradually from the shore and diminishes in velocity. On striking the banks of Newfoundland, it turns a little to the south, but still reaches the north-east coast of Europe. This is evinced by the fact that the productions of tropical America are often cast upon the coasts of Scotland and Norway. On reaching a point a little to the west of the Azores, this stream turns to the south and proceeds to the Canaries, again to mingle its waters with the great Equatorial current. Humboldt believes, from the dates of letters contained in bottles, and other objects thrown on shore on the African islands, that the Gulf. Stream completes its circuit in a period of from two to three years. Its velocity diminishes gradually from 5 miles to 1 per hour, and its temperature from 87° to

720, in its extensive tour of the Atlantic. In its course southward, this stream throws off the two following lateral currents :

20. Rennell's Current, which passes along the northern coast of Spain into the Bay of Biscay, with the velocity of 1 mile per hour. It then turns north along the coast of France, increasing in velocity to 3 miles per hour, and spreading to a breadth of more than 100 miles, until it crosses the mouth of the English Channel, and strikes the southern coast of Ireland.

The North African and Guinea Current begins about lat. 45° N., and flows towards the north of Africa; a portion runs constantly into the Mediterranean Sea through the Straits of Gibraltar, sometimes with such force that ships are compelled to await an easterly wind to sail out against it; the other branch runs close along the western coast of Africa into the Bight of Benin.

21. The South connecting Current. This is produced by the Drift Current of the south-east trade wind, and flows towards the Cape of Good Hope, whence it divides, one branch turning into the Atlantic, and the other passing into the Indian Ocean.

The Arctic Cold Current is formed by two currents, one flowing south-west between Iceland and Greenland, and the other flowing from Hudson's Bay and Davis's Straits towards the east. They unite south of Greenland, and run into the Gulf Stream in lat. 44° N., off the east of Newfoundland. These currents bring down vast fields of ice, which sometimes reach the Gulf Stream, especially in the month of May. They also throw vast quantities of drift-wood on the coasts of Iceland and Greenland, which furnish important supplies of fuel.

22. When two opposing tides meet, they often produce whirlpools; the most remarkable one known is the Maelstrom, on the coast of Norway. In a storm it roars with tremendous noise, and its influence is felt at a distance of 9 miles from its centre. The whirlpool of Charybdis, in the Straits of Messina, was the terror of ancient mariners.-EDWARD HUGHES.

Biography.

LESSON I.

LIFE OF JAMES WATT.

BY HUGO REID.

1. MANKIND do not find everything they want lying around them ready made to their hands, in the state in which they require it for use. Most things need to have some change wrought upon them to adapt them

to our wants, and many things have to be brought to us from a great distance, even from the furthest parts of the earth. The soil must be turned up by the plough, the chaff must be separated from the grain, and the corn must be ground. Wool, cotton, and flax, must be spun into thread, and woven into cloth; water and coal

must be raised from considerable depths in the bowels of the earth; and tea, sugar, cotton, silk, indigo, and many other useful articles have to be brought from fardistant places.

2. For all such operations we require force, that is, the means of producing motion. We must carry, lift, press, turn, or subject to some description of motion, the object which needs a change effected upon it to render it fit for our purposes. In a rude state of society, the only available force is the muscular power of animals, either of man himself, or of some of the lower animals, as horses and oxen: in some countries even at this day, the inhabitants have no other means of producing motion; and are, therefore, very imperfectly supplied with those comforts and conveniences which abound among civilized nations. But when the useful arts had made some little progress, ingenious men, observing that water falls with force, and flows with force, and that wind blows with force, contrived machinery which they interposed between these natural forces and the objects to be acted upon, and thus arose the various kinds of water-wheel, the windmill, and the ship, spreading its sails to the breeze, instead of being urged on laboriously and slowly by oars. These are very old contrivancesso old, that we have no records whatever of the dates of the inventions, nor of the names of the inventors.

3. About a hundred and fifty years ago a new power came into use, quite different in its nature from any of those previously employed, which has now almost superseded the use of the former sources of motion, and proved far more effective than all of them put together. It is procured by the simple operation of making water boil; and the machine by which it was brought into action was called the fire-engine, or steamengine. When water boils, that is, is converted into steam, it occupies about 1696 times the space which it did when in the form of water, and in the act of so expanding, presses with very great force on all the bodies surrounding it, and will burst the vessel which contains it if it be confined; or may be made to impart motion to bodies properly adjusted for the purpose.

Men had long known vaguely that water expands with force when turning into steam. They had seen a small quantity of water formed into a large volume of steam; they had seen the jet of steam which rushes out with force from a boiler; they had seen the lids of boilers violently raised by the force of the confined steam; probably the bursting of boilers when the steam had no outlet was not unknown to them. So long ago as one hundred and thirty years before the commencement of the Christian era, HERO of Alexandria gave a description of a sort of toy-machine moved by this force, called the colipile; but it was not proposed to be applied to any useful purpose. Steam-engines on the same plan have recently been made, but they have not been found to work economically. After the revival of arts and letters, DE CANS, BRANCA, the MARQUIS of WORCESTER, DENIS, NAPIER, and others, made suggestions or endeavours to apply the power of steam to useful purposes. THOMAS SAVERY, in the year 1698, took out a patent for a steam-engine which he invented; and several of his fire-engines were actually erected and employed in raising water from mines-the first steamengines which were applied to do useful work. But they were costly and dangerous. There is a tradition, that at Barcelona, in the year 1542, a Spanish naval officer, BLASCO DE GAVAY, had propelled a vessel without oars or sails by some machinery, of which a large kettle, filled with boiling water, was a conspicuous part;"-if true, an extraordinary invention at so early a period. But the first steam-engine capable of doing any useful work with safety and economy, was that now called the atmospheric engine, or Newcomen's engine, invented by NEWCOMEN and CAWLEY, two mechanics of Dartmouth, who took out a patent for it in the year 1705; soon after which it was used in many places to drain the mines, and continued during the greater part of the century to be the machine most in use for the purpose of raising water, whether for the supply of towns, or clearing the mines from the water, which always tended to accumulate, and to impede or prevent the operations of the miners.

66