The Grand Canal of New-York, presents several examples of this kind, which exhibit, in a striking manner, the powers of modern art.

418. In passing mountains and hills, which cannot be avoided, or cut down, subterranean passages are sometimes dug through then, which are called tunnels. The water is conducted through them, so that boats can pass on without interruption; and the traveller seems to enter the bowels of the earth.

An excavation of this kind in a branch of the Duke of Bridgewater's Canal, is nearly a mile in length, through a solid rock, in some places 120 feet below the surface. Those of the Canal of Languedoc, are only 375 and 543 feet in length, and 9 feet in diameter.

419. Canals are usually carried over heights of land by less expensive means. The canals of China are rendered navigable on declivities, by means of floodgates, which form a temporary dam. They raise the water to a considerable height on the top of the declivity, and are opened at stated hours in the day, when the boats collect, and are allowed to pass down the torrent formed by the accumplated waters. Where the declivity is too great to admit of this, they are obliged to resort to powerful engines, by which the boats are drawn up along an inclined plane, and let down in the same manner.

420. In European canals, great improvements have been made by the use of locks. These are no more than a succession of tight reservoirs, or basins of water, built on the declivity, one a little below the other, which are closed by flood-gates at both ends, and are alternately filled and emptied to enable the boats to descend gently.

421. In descending, the water of the first lock is gradually let off into the second, until the water, and the boats upon it, sink to the level of the second. The floodgates are then opened, and the boats of the upper lock pass into the second, The waters of the second then flow into the third, until they are on the same level, and the boat passes without any shock or danger into the third; and so on to the bottom of the declivity.

In the same manner a boat may pass in the opposite direction, from the lower lock to the second; and may gradually rise to the summit of the hill, without any exertion of force. This is repeated whenever a boat is to pass, and renders the navigation easy and safe.

422. Canals are often constructed around the falls and rapids of rivers, to aid in their navigation. But they are frequently formed along the banks of unobstructed streams, in order to avoid the inconveniences arising from the droughts of some seasons, and the floods of others, and the uncertainty and danger of a navigation depending on winds and currents.

423. The Imperial Canal of China is the most extensive monument of human industry, of this kind, in the world. It extends 500 miles, from the neighbourhood of Pekin to the Yellow River. At its entrance into this stream, it is three quarters of a mile in width. Its construction, however, is very imperfect,

424. The longest canal in Europe is that of Languedoc, in France, which [62] connects the Mediterranean Sea with the River Garonne. The whole distance is 140 English miles, and it is navigated by boats of 100 tons. It passes one ridge, through a tunnel 543 feet in length.

425. The Canal of the Centre, in France, uniting the Saone to the Loire, is 71 miles long. About 4,000 boats pass annually.

The Canal of Burgundy, uniting the Saone to the Seine, which is partially completed, will be 148 miles in length. The Canal of Picardy, forming a part of the navigation from the Scheldt to the rivers of France, is remarkable for two tunnels, one of which is more than 3 miles in length, and 26 feet in width.

426. The Canal of Kiel, or Holstein, passes across the isthmus of Denmark, from the Baltic to the North Sea. It is the largest on the continent; admitting sea vessels of 120 tons, and sometimes 2000 in a year.

427. There are several canals which connect the rivers of the Baltic with one another, and with those of the Caspian and Black Seas. But they are generally of no great length; and passing through a level country, are destitute of any remarkable exhibitions of skill or labour. The longest is the Canal of Ladoga, which passes more than 60 miles, along the bank of that lake, in order to avoid the irregularities of its navigation.

428. England is not excelled by any other country, for skill and enterprise in the structure of canals. More than 2,400 miles of artificial navigation have been formed, in various parts of the kingdom.

429. One of the principal canals, is the Grand Trunk, which passes from the River Mersey, 99 miles to the Trent, near the centre of the kingdom; and thence, 40 miles to the Severn; making in the whole about 140 miles. From the Grand Trunk, the Oxford Canal extends 90 miles to that city. From the upper part of the Oxford Canal, a branch of 100 miles is carried into the Thames, a short distance above London; which connects this metropolis with the great system of artificial navigation in the interior, and is called the Grand Junction.

The Ellesmere and Chester Canal, connects the Rivers Mersey, Dee, and Severn, by two lines, crossing each other. It contains an aqueduct of iron, 1,000 feet long, and 126 feet high; probably the largest ever constructed.

430. In Scotland, the Caledonian Canal, which connects the Murray Frith on the eastern coast, with the Atlantic Ocean, is 59 miles in length, (37 of which are in natural waters,) and is navigable for frigates of 32 guns. The Forth and Clyde Canal admits vessels which draw 8 feet of water. The whole expense of this canal was only 200,000l., and the annual revenue varies from 40,000 to 50,0007. 431. The Grand Canal of Ireland extends from the Liffey, at Dublin, 83 miles, to the River Shannon. The Royal Canal, which is north of this, extends in a parallel line, seldom 10 miles distant from it, from Dublin to another portion of the Shannon. There are several branches extending to various rivers and towns, by which the capital is connected with the western and southern coast, and principal towns of the kingdom.

432. In the United States, the Middlesex Canal, was the first of any magnitude. It was commenced in 1790. It passes across the peninsula between the Merrimac River, and Boston Harbour, a distance of 31 miles. It admits boats of 14 tons, which are drawn by one horse, 3 miles an hour. Packet boats pass down the whole length in 5 hours, and go up in 7.

433. The next canal of importance, executed in the United States, was from the Santee to the Cooper River, in South Carolina. It is 22 miles in length, and [63] admits boats of 20 tons. The Great Dismal Canal, passing through the swamp of this name, in North Carolina, is not entirely executed; but even now, proves very useful.

There are several canals in the flat alluvial delta of the Mississippi, intended to connect its various channels.

434. The third extensive canal finished in the United States, was the Northern Canal of New-York, from Whitehall, on Lake Champlain, to Fort Edward, on the Hudson. It passes in part through the channels of small streams, and the navigation is extended around the obstructions in the Hudson River, to Álbany. 435. The most important canal in the United States, and the longest in the world, except the Imperial Canal of China, is the GRAND WESTERN CANAL Of New-York. It passes along the Mobawk River, generally above its level, to Rome; and thence westward, across the bead of the small lakes, and over the Genessee River, to Lake Erie, at Buffalo.

It rises about 526 feet above the level of the Hudson River, and contains in the whole about 80 locks, with several considerable embankments and aqueducts. It was commenced in 1817, and finished in 1825.

436. A number of short canals have been constructed at the falls of rivers in the United States. The navigation of the Connecticut, the Potomac, the James, and other rivers have been considerably extended by this means.

Some of the most interesting works of this kind are on the Connecticut River, at South Hadley. The upper fall is passed by a canal; the lower by means of an inclined plane of stone. A car with wheels is sunk beneath the boat in the lower canal, and is then drawn up by means of a water wheel, and landed in the upper canal in 15 minutes.

437. Canals have been commenced to unite Delaware River with the Hudson and Susquehannah, and Delaware Bay with the Chesapeake. Others are also. proposed in various parts of the country.

A more particular account of the various lines of canal navigation, will be given under the head of Inland Navigation, in the account of the grand divisions of the

world. The following table exhibits the size and greatest elevation of the principal canals in the world.

[64]

GRAND DIVISIONS OF THE EARTH.

-438. The Grand Divisions of the Earth are also natural divisions. South America and Africa are obviously mere projections of their respective continents; the former connected only by the sand-hills of Suez; the latter, by the rocky isthmus of Darien. Europe also is evidently a distinct projection of Asia; although the breadth of the land at its union renders it difficult to assign a satisfactory boundary; and Asia remains as the nucleus or centre of the old world.

The English Geographers have generally considered the boundaries of Europe as formed by the Ural Mountains, the Volga, and the Don; but the more natural and distinct course seems to be by the Ural Mountains and River to the Caspian; and from the southern extremity of this sea, by the boundary of the Russian Empire, to the Black Sea. By this course we embrace Georgia and Circassia, where the European race exists in the greatest perfection, and whence, perhaps, it originated.

The Eastern Continent is distinguished for the antiquity of its empires and cities, and the splendour of its works of art. But the Western Continent is most remarkable for the magnificence of its natural features; and excels all other divisions of the world in the grandeur of its mountains, lakes, rivers, and cataracts.

The following articles contain a connected description of the surface and natural features of each of the grand divisions, agreeably to the physical boundaries, marked by seas, mountains, and rivers.

(20.) Physical Sections of South America, from east to west. I. Northern Part.- II. Southern Part.

439. SOUTH AMERICA has a very irregular surface, and embraces some of the loftiest mountains, the most extensive plains and basins, and the largest rivers in the world.

440. The Andes, and their subordinate chains, give character to the whole surface of South America. The principal chain runs from north to south, its distance from the shores of the Pacific Ocean varying from one to two hundred miles; and appears to continue, as already stated, through the Isthmus, along the coast of North America. Its height is by no means uniform. In some places it rises to more than 20,000 feet, while in others, it sinks to less than 1,000 feet above the level of the sea. The whole range seems based upon volcanic fires, and numerous peaks are continually burning.

441. This vast trunk sends forth several branches towards the east, in the southern part of the continent, nearly at right angles to its principal direction. The most celebrated of these secondary chains is that which stretches along the northern coast of South America, towards the island of Trinidad, and is often called the Chain of Venezuela. Its summits, according to Humboldt, are from 14,000 to 15,000 feet in height.

442. The second, or middle of these chains, leaves the main ridge between the third and sixth degrees of south latitude, and stretches towards the east to an unexplored extent, though it has been traversed for about 600 miles. Its highest points are inferior to those of the former ridge.

443. The third lateral branch makes almost a semi-circular sweep between 15 and 20 degrees of south latitude, passing through the province of Chiquitos, and is hence called by Humboldt the Cordillera, or chain of Chiquitos. It appears to connect the main body of the Andes with the mountains of Brazil and Paraguay, supplying the rivers that feed the Amazon from its northern declivity, and the branches of the La Plata from the southern. Its precise direction, elevation, and structure, are but imperfectly known.

444. Different portions of the Andes present the greatest diversity of aspect and character. In some parts, the vast summits constitute only one ridge; but in others they are arranged in two or three. In Chili the breadth of the Andes is about 120 miles, forming one compact chain. In Peru, they divide into three distinct and parallel chains, which continue to about the sixth or seventh degree of south latitude. In the province of Quito they form only two ridges, which unite further north. The distance of the western ridge from the sea here exceeds 100 miles; the erests are seven or eight leagues from each other; and the plain that separates their bases is five or six leagues in width. Within this narrow limit a vast population is concentrated, and towns have been built containing from 30,000 to 50,000 inhabitants each.

445. The principal ridge of the Andes generally rises abruptly, with numerous and frightful precipices, hiding its lofty summits in the clouds, or rising with awful majesty into the pure regions of the air above them. They are remarkable for the number of immense chasms, termed quebradas, which are found among them. They are covered with perpetual snow; but the [66] uniform temperature of the equatorial and tropical regions prevents the formation of glaciers. Their declivities present all the varieties of climate and productions found upon the globe.

PHYSICAL DIVISIONS.

446. By means of the Andes and their branches, South America may be considered as divided into five principal parts-the western declivity--the basin of the Orinoco-the basin of the Amazon-the basin of the Paraguay--and the southern extremity.