GRAND DIVISIONS OF THE OCEAN.
The ocean is subdivided into portions, which are known by different names, viz. the Atlantic, Pacific, Indian, Arctic or Northern, and Antarctic or Southern oceans. The situation of these may be seen by reference to the map of the world.
The Atlantic ocean varies in extent, from seven hundred to four thousand miles in breadth from west to east, and is nine thousand miles in length.
The Pacific ocean extends from north to south about eight thousand miles, and from west to east about eleven thousand miles,—almost half round the globe.
The Indian ocean extends from north to south about four thousand miles, and from west to east varies from twenty-five hundred to six thousand miles.
The Northern ocean is encircled by the coasts of the two continents. Its greatest extent in one direction is computed to be three thousand miles.
The Southern ocean lies south from the Atlantic, Pacific, and Indian oceans, and surrounds the south pole.
The most remarkable phenomenon which occurs throughout the extent of the ocean is the Maelstrom. This is a whirlpool by which a ship or any thing which comes within the reach of the circling current is swallowed up.
THE MAELSTROM.
This whirlpool is in the Atlantic ocean, near the coast of Norway, Europe.
MOUNTAINS, &c.
Mountains form the principal feature which presents itself on viewing the surface of the land. These immense heights have their descents, more or less steep, and their exteriors greatly diversified. Some of them present a surface of naked and rugged rocks piled one upon another; others show an abrupt and almost perpendicular surface, which conveys to an observer an idea that the mountain has been cut from top to bottom, so as to show the interior. Sometimes mountains seem, when viewed from particular points, to show the form of the head of a tiger, a bear, a man’s face, &c.
Some are composed of columns of basaltic rock, so regularly formed and disposed that they seem to have been formed by art. The columns are five or six sided, and appear to be divided into joints, at intervals of about thirty feet. The Giant’s Causeway in Ireland, is a remarkable instance of this natural curiosity.
GIANT’S CAUSEWAY.
At this place there are ranges of these columns which extend into the sea several hundred feet, and their tops present an almost level surface of pavement.
Mountains have often large cavities in their interiors. In Norway, Europe, there is a remarkable instance of a singular natural formation of a mountain. Mount Torghat is pierced through with an opening one hundred and fifty feet high, and three thousand long; at certain seasons of the year the sun lights up the interior of this passage from one end to the other.
Defiles or passes are narrow natural openings or roads through a chain of mountains, and often form the only communication from one part of a country to the other. There is a famous defile of this kind at the Cape of Good Hope, Africa, which is called Holland’s Kloffe.
HOLLAND’S KLOFFE.
This pass is so situated that it forms the only communication from the country of the Hottentots to the country beyond the mountains. One hundred men could here successfully oppose the march of an immense army.
A defile sometimes forms the bed of a river, by which means the stream passes through a chain of mountains. In the United States there is an instance of this, where the opposite sides of the defile are connected together at the top by a natural bridge of rock.
NATURAL BRIDGE, VIRGINIA, U.S.
A Plateau is a plain of immense extent, which is formed of an extensive surface of elevated land. Some plateaus are eight thousand feet above the level of the sea. Lofty mountains often rise from these plateaus, many of which are volcanic.
Volcano is a word taken from the name which the Romans gave to the God of Fire. It now designates those mountains which are subject to eruptions of fire, smoke, stones, and lava. The irruption of a volcano is a most awful and majestic phenomenon. The earth is shaken, and rumbling noises are heard, which sound like thunder. Smoke and fire begin to issue from the top of the mountain.
Suddenly the fire becomes extinguished, and red-hot stones are thrown out; then the crater is filled with a burning liquid called lava, which looks like metal in a melted state. At last, the lava overflows the sides of the crater, and runs down the sides of the mountain, destroying every thing which lies in its path, and covering cities and cultivated fields with a sea of burning matter. Sometimes the lava is too heavy to be elevated to the summit, and bursts out from the side of the mountain.
CRATER OF MOUNT ETNA.
The cities Herculaneum and Pompeii, in Italy, were entirely destroyed, A. D. 79, by an irruption of Vesuvius.
Herculaneum was discovered by digging away the ashes and lava, in the year 1713. Pompeii was discovered about forty years afterwards.
The height of mountains is measured from the level of the sea.
The highest mountains in the world are the Himmaleh mountains, in Asia.
The second in point of elevation are the Andes mountains, in South America; Chimborazo is the highest peak.
The highest mountain in North America is Mount Elias,—in Europe, Mont Blanc,—in Africa, the Atlas mountains.
A traveller in South America has lately asserted, that he has discovered a mountain in Peru, which is higher than the Himmaleh mountains in Asia. If this be a fact, it will probably soon be confirmed by the testimony of other travellers.
The highest volcanic mountain in the world is Cotopaxi, one of the Andes, in South America. Other celebrated volcanoes are Popocatepetl, in North America,—Mount Etna, Stromboli, and Vesuvius, in Europe,—and Mount Hecla, in Iceland.
Mountains are sometimes found standing alone; but generally many of them are united in a range, or ridge, which extends many miles, and, in some instances, through the whole extent of a continent.
In ascending mountains it will be found, that as you proceed towards the top, the climate grows continually colder; and after passing beyond the height of about 17,000 feet from the level of the sea, you arrive at a region where snow and ice cover the ground during the whole year. This contributes much to the coolness and salubrity of the climate of countries where such high mountains are found.
COMPARATIVE HEIGHTS OF MOUNTAINS.
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COMPARATIVE LENGTHS OF RANGES OF MOUNTAINS.
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Small streams are called Brooks, Rivulets, and sometimes Creeks. In the study of the maps they are called branches of rivers.
Many small streams, being formed in the mountainous and other elevated parts of a country, flow together, and form a large current of water which takes the name of a river, and is constantly augmented in its course, by other brooks, &c. and by rain, until it discharges itself into an ocean, sea, lake, or some other river.
The length of rivers has not been so definitely ascertained as the height of mountains. The length of the same river varies in the statements of different geographers, and this difference is owing to the principles on which their measurements are made, some measuring the windings of the river, and others only the valleys through which they flow.
The longest and largest river in the world is the Amazon, in South America. It is more than 150 miles wide at its junction with the Atlantic ocean. The body of water is so great that it constantly flows into the ocean, and is not affected by tides. The commotion caused by the meeting of the tide and the current of the river, sometimes renders navigation dangerous.
The longest rivers in North America are the Missouri and Mississippi.
The longest river in Asia is the Kian Ku. In Europe, the Volga. In Africa, the Nile.
The Missouri flows into the Mississippi about 1300 miles from its mouth, and is, in fact, the main river. And the length of the Missouri is given, in the opposite table, from its source to the mouth of the Mississippi.
The Missouri and Mississippi rivers, taken together, have no rival in the world, for length of course, the size and number of their tributaries, and the vast extent of country through which they flow. The Mississippi is called by the native Indians the ‘Father of Waters,’ and the Missouri, the ‘Mother of Floods.’
COMPARATIVE LENGTHS OF RIVERS,
ACCORDING TO THE BEST AUTHORITIES.
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Rivers are supplied with water principally from springs, and the melting of snow upon high mountains. Mountains attract clouds around their tops and sides, and by this means become saturated with water, which, finding its way through the fissures of the rocks, forms springs. In this manner probably all springs are formed, whether they are found on mountains or plains. Heavy rains also augment the quantity of water, and often after a heavy fall of rain, many rivers are so swollen that the water overflows their banks, and the flood sweeps away every thing that is within its reach.
The Mississippi is subject to inundations during the spring, and the banks of the river being higher than the adjacent country, the water never returns to the river, but seeks other channels. These inundations greatly enrich the lands.
The banks or shores of rivers present very different appearances, according to the formation of the land through which they pass. The banks of some rivers are but little elevated above their level, and slope gently down to the water’s edge; others flow through rocky channels, and are walled on each side with high and almost perpendicular precipices.
PASSAIC FALLS, NEW JERSEY, U. S.
Sometimes a precipice occurs immediately across the course of a river, and the water falling nearly perpendicularly over, forms a cataract or falls.
They are often obstructed by rapids which render navigation difficult and sometimes impracticable. A rapid is a gradual descent in the bed of a river, where the current is swift, and the water shallow.
Some rivers suddenly disappear, by flowing into a chasm, and are lost in the earth. Some of these again issue from the earth at a great distance from where they disappeared.
Rivers present obstacles to the route of roads, and many expedients have been invented by the ingenuity of man to obviate them. In many places bridges are built of wood, stone or iron; and where the current is too swift, or the channel too deep to permit a bridge to be built, the passage is made in boats. But the most astonishing project that has been undertaken for this purpose is the Tunnel under the river Thames, at London, England. A road is here dug out under the river, and is nearly completed. A view of the work is given in the cut.
THAMES TUNNEL.
The tunnel consists of two brick archways for carriages, and two foot paths. The passages are divided by a line of arches, between the pillars of which are placed gas lights. This undertaking was commenced in the year 1825. The whole length is thirteen hundred feet, and each archway is about fourteen feet in width. The thickness of the earth between the bed of the river and the tunnel is about fifteen feet.
A country, possessed of large and navigable rivers, enjoys a great blessing. They form a means of internal communication, by which the productions of the inland country are brought to the city and seaport. Their currents are made use of, by the aid of machinery, to manufacture many of the necessaries and luxuries of life.
Many rivers whose waters are pure, afford water for the use of the inhabitants of neighboring cities.
London and Westminster, England, are supplied from the New river; the water is here brought thirty-eight miles through a canal. The Schuylkill river in Pennsylvania, United States, supplies the city Philadelphia with good and wholesome water, for the use of the inhabitants.
VIEW OF THE PHILADELPHIA WATERWORKS.
These works are ingeniously constructed at Fair Mount on the eastern bank of the river. The water is raised by the action of an engine, moved by the water power of the river itself, and deposited in large reservoirs, from whence it is conveyed by iron pipes to every part of the city. The aggregate length of the pipes already laid exceeds 63 miles. Three reservoirs have already been constructed which contain ten millions of gallons, and a fourth has been commenced which will contain ten millions more, being a quantity sufficient for the use of the city Philadelphia ten days.