Relative Size of Lakes of the Western Hemisphere
Relative Size of Lakes of the Western Hemisphere
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PRINCIPAL SALT-WATER LAKES OF THE WORLD
Relative Size of Lakes of the Eastern Hemisphere
Relative Size of Lakes of the Eastern Hemisphere
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PRINCIPAL FRESH-WATER LAKES OF THE WORLD
Africa.The great plateau lakes are typical of the continent. The Victoria Nyanza and Albert Nyanza, feeding the White Nile; Tanganyika, whose outlet is unknown; Tzana, at the head of the Blue Nile; and Lake Nyassa, in the Zambezi basin, all rest on the high plateaus of Central Africa. Lake Tchad alone, among large African lakes, is surrounded by low plains.
Waterfalls and Rapids.The variations in the slope of a river-bed, arising from unequal erosion, or from the original irregularities in the surface, give rise to rapids and falls.
The first occur where an increased slope causes the stream to flow with more than its average velocity. The second are caused by nearly perpendicular rocky walls, down which the foaming water descends in picturesque cascades, or imposing cataracts.
The famous “Cataracts of the Nile” are merely rapids which impede but do not entirely obstruct, the navigation as cataracts must. The so-called Falls of St. Anthony, in the upper Mississippi, and the rapids of the St. Lawrence, above Montreal, are among the finest rapids in American rivers.
The highest falls are in the upper course of rivers, in mountainous regions; the greatest and most imposing, in their middle course.
The Niagara Falls exhibit a most important industrial utilization of water power. The Falls of St. Anthony in the Mississippi, the Falls of Foyers in Scotland, the Rhine falls, the Rhone falls of Bellegarde, and the innumerable waterfalls of Scandinavia, Switzerland, and similar mountainous lands, are all utilized in this way. It has been proposed to convey power generated at the Victoria falls of the Zambezi to the Rand goldfield of the Transvaal, and a scheme for this is now being prepared.
FAMOUS WATERFALLS OF THE WORLD
FAMOUS WATER PICTURES OF THE NEW AND OLD WORLD
Niagara in winter presents a picture of frozen grandeur equaled nowhere else in the world.The Rhine at Schaffhausen, Switzerland, rushes over rugged rocks on its way down from the highlands into the lovely and historic valley it has carved for itself on its way to the sea.
Niagara in winter presents a picture of frozen grandeur equaled nowhere else in the world.
The Rhine at Schaffhausen, Switzerland, rushes over rugged rocks on its way down from the highlands into the lovely and historic valley it has carved for itself on its way to the sea.
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FAR-FAMED WATERFALLS THAT HAVE INSPIRED TRAVELERS AND WRITERS
1. TheNiagara Fallsand rapids form one of the most impressive spectacles in the world. The Niagara River, which is the sole outlet of the great lakes, pours itself in two vast sheets over a precipice about 160 feet high. Goat Island, which is situated on the lip of the falls, divides the cataract into two sections—the Horseshoe, or Canadian fall, which is by far the more majestic, and the America fall. It has a descent of 158 feet and the American fall of 167 feet. The volume of water which sweeps over this immense chasm is about 15,000,000 cubic feet per minute. The limestone edge of both falls is wearing away in the center, the Canadian fall now being V-shaped, and the American fall showing the same tendency, although its process of recession has begun more recently. For some distance below the falls there is smooth current, the mass of water which pours over the precipice sinking and only coming to the surface two miles below, where the rapids, more magnificent and wilder than those above the falls, begin, and culminate in the rapids of the Upper Whirlpool. Lower down the river is the whirlpool itself, where a sharp turn sends the waters hurling against the Canadian side; they then sweep round in a gigantic circle before they find a vent at right angle with their former course. The sight of the falls is equally awe-inspiring from the bridge on the lip of the fall, from the boat which plies from shore to shore below the cataract, or from the Cave of the Winds, reached from Goat Island. Although in summer the magnificence of the sight is extraordinary, it is in winter, when the wizardry of the frost is upon it, that it is superlatively beautiful. The falls were first discovered by Father Hennepin in 1678.
2. TheFalls of Juanacatlan(hoo-ă-nă-kwt-lăn), Mexico, are located near the island city of Guadalajara (guă-dă-lă-hă´ră) on the Rio Grande de Santiago. Though only 70 feet in height they are more than 600 feet wide, and as known as the “Niagara” of Mexico.
3. TheCataracts of Iguazu(e-gwă´soo) on the frontiers of Brazil, Argentina and Paraguay. These falls, situated in a remote wilderness, far from civilization, are a veritable fortress in protecting the peace-loving peoples on their borders. They constitute a series of falls extending over three miles, and more than 200 feet in height, and of magnificent scenic beauty. Their energy is estimated to be about 14,000,000 horse-power, or almost three times that of Niagara.
4. TheYosemite(yo-sem´i-tee)Fallsof California, are highest and probably the most remarkable of their class. They descend on almost perpendicular ledge of rocks 2,600 feet high to the bottom of the Yosemite valley, forming three separate cataracts. The first fall is 1,600 feet sheer descent. Then comes a series of cascades, partly hidden, 600 feet downward, and a final leap of 400 feet. Seen from afar, the Yosemite Falls seem insignificant; but they are, in fact, 35 feet wide, and the shock of their descent is observed a mile away.
5. TheStaubbach(stoub´băk)Falls, in the Swiss Alps near Lauterbrunnen, descends a precipice of 980 feet, and is reduced to spray like a misty veil before reaching the bottom. It is the highest unbroken fall in Switzerland, and the most noted.
6. TheGreat Falls of the Yellowstone, though not so high, vie with the Yosemite in striking beauty. These famous falls plunge from a height of 360 feet into the abyss of a mighty chasm. At the point of descent, the waters of the Yellowstone suddenly contract from a width of 250 feet to 75 feet.
7. TheBridal Veil Fallsof California, belong to the famous Yosemite Valley. Its waters, over 30 feet wide, leap from the granite rocks on the south wall of the Yosemite in two vertical descents aggregating over 900 feet. The first fall covers a distance of 600 feet, then the waters rushing over a sloping pile of jagged rocks drops a perpendicular distance of 300 feet more. From the chief points of view it seems to make but one plunge, in an unbroken descent similar to the Staubbach, but carrying a much greater volume of water. Frequently the wind swings the great plume of water from the face of the cliff and waves it like a scarf or veil. At sunset rainbows with an indescribable radiance bejewel its foam and the glistening leaves surrounding it.
8. TheReichenbach(ri´ken-băk)Fallsnear Meiningen, Switzerland, comprise five fine cascades in the Reichenbach River. The most gorgeous of these, known as the Upper Fall, makes a huge leap of 300 feet into a deep rocky basin, which then continues in several foaming and plunging cascades in general aspect not unlike the Niagara gorge.
THE LAND AND WATER HEMISPHERES
THE LAND AND WATER HEMISPHERES
The Oceans consist of one great fluid mass, and in extent covers three times the area of the dry land. There is also about three times as much land to the north of the equator as there is to the south of it. Though the waters of the ocean surround the land on every side, yet they are broken up into certain areas by the arrangement of the land portions, and to these various parts we give particular names.
The Atlantic Ocean, lying between the western shores of Europe and Africa and the east coast of America.
The Pacific Ocean, lying between the west coast of America and the east coast of Asia.
The Indian Ocean, lying between the south of Asia and the Antarctic circle.
The Arctic Ocean, lying within the Arctic circle.
The Antarctic Ocean, lying within the Antarctic circle.
The Atlanticis the most branching of the oceans, and is especially distinguished by the number and great size of its inland seas. Two of these, the Mediterranean Sea and the Gulf of Mexico, lie in the warm regions; and two, Hudson Bay and the Baltic Sea, in colder latitudes.
The broader seas are represented by the Caribbean Sea, within the tropics and the Gulf of St. Lawrence and the North Sea in temperate latitudes. The Gulf of Guinea, and the Bay of Biscay, are examples of the more shallow coast waters.
The Pacificis particularly rich in vast border seas, a continuous series of which lines the Asiatic and Australian coasts. Among these are the Behring Sea, enclosed by the peninsula of Alaska and the Aleutian Islands; Okhotsk Sea, enclosed by Kamchatka and the Kurile Islands; the Sea of Japan, and the North and South China seas; and the Arafura, Coral, and New Zealand seas, on the Australian Coast.
Only two inland seas of considerable size—the Gulf of California in North America, and the Yellow Sea in Asia—mark this entire basin.
The Indian Oceanis characterized by gulfs, two of which form the entire extension of the basin; namely, the Gulf of Bengal, and the Arabian Sea. It has also two inland seas of considerable extent, the Red Sea and the Persian Gulf, isolating the peninsula of Arabia from the adjacent continents; but border seas are wholly wanting in the Indian Ocean.
The Arctic Oceanis a partially enclosed sea, which a comparatively inconsiderable rise of the sea-bottom would convert into a true Mediterranean. Three openings connect it with the Pacific and Atlantic Oceans, namely, Behring Straight (narrow and shallow), Davis Straight, and the broad expanse of water lying between Norway and Greenland. Of these, the last is by far the most important, for through it the warm waters of the Gulf Stream find access to the Polar basin, and keep the sea free from ice throughout the year. This current is supposed to flow feebly along the coast of Siberia, until, deflected by the land, it becomes merged in the cold counter-currents which, passing along the eastern coasts of Greenland and Labrador, carry immense masses of ice into the Atlantic.
PICTORIAL DIAGRAM OF THE STRUCTURE OF THE EARTH IF THE WATERS WERE REMOVED
MapSectionRidges, mountains, plateaus, which may represent submerged continents of the past, and many an abyss that exceeds in depth the height of the highest mountains, are shown above. The shallow coasts, marked by the lightest shade, are part of the present Continental Shelf, and do not exceed six hundred feet in depth. Beyond this shelf, as a rule, the oceans rapidly attain great depths. Our knowledge of the ocean bed has been obtained from the extensive soundings.
Ridges, mountains, plateaus, which may represent submerged continents of the past, and many an abyss that exceeds in depth the height of the highest mountains, are shown above. The shallow coasts, marked by the lightest shade, are part of the present Continental Shelf, and do not exceed six hundred feet in depth. Beyond this shelf, as a rule, the oceans rapidly attain great depths. Our knowledge of the ocean bed has been obtained from the extensive soundings.
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The Antarctic Oceanis situated about or within the antarctic circle. The great Southern Ocean is that part of the ocean which surrounds the world between the latitude of 40 degrees south and the antarctic circle. The northern portions of this band are often called the South Atlantic, South Indian and South Pacific, while the southern portions are usually called the Antarctic Ocean. The average depth of the continuous ocean which surrounds south polar land is about two miles; it gradually shoals toward antarctic land, which in some places is met with a short distance within the antarctic circle. Life is abundant in the surface waters, and at the bottom of the ocean.
As a rule the sea is shallowest near the land, though in a few cases there is a sudden descent to a great depth at a very short distance from the coast. Lowlands have usually shallow seas near the coast, and highlands deep water.
Along the American shores, in the latitude of New York, the depth, for a distance of more than 100 miles, is less than 600 feet; then suddenly the bed descends, by a steep slope, to the depth of 6,000 or 9,000 feet. After a comparatively narrow interval, a second terrace descends to the main basin, from 15,000 to 18,000 feet deep.
The bottom of the trough of the ocean, in general, is equally varied with that of the land surface of the globe, forming mountains, hills, valleys, tablelands, etc. In many parts these marine mountains reach above the surface and form islands. On the table land extending across the Atlantic between Newfoundland and Ireland is laid the submarine-telegraph cable which connects the two hemispheres.
The Depth of the Oceans.The average depth of the Pacific Ocean has been estimated at between 15,000 and 18,000 feet, which is slightly greater than that of the Atlantic. The deeper portions may be learned on reference to themap. The western portion of the North Pacific in particular shows some very deep depressions. To the east of Japan lies a long deep trough which in one part has furnished the sounding of nearly five and one-half miles. This abyss is often called the Tuscarora Deep. South of the Ladrone Islands, in the Caroline Archipelago, there is also a deep abyss where an English ship, theChallenger, obtained a sounding of nearly 27,000 feet. In the Pacific soundings of over 30,000 feet have been made.
The Indian Ocean has an average depth of about 12,000 feet, and the deepest soundings have been taken on the eastern side. It is interesting to observe that the deepest sounding, about five and three-quarter miles, in the South Pacific somewhat exceeds the height of the highest mountain. Mount Everest has a height of 29,000 feet above the sea level. And it must also be noted that the mean height of the land, 1,000 feet, is only about one-twelfth the mean depth of the whole ocean, 12,000 feet. (Seecolored mapshowing comparative surfaces of land areas and ocean depths.)
Inland and Border Waters.These enclosed basins belong to the structure of the continents, rather than to the oceans. All are shallow in comparison with the great basins with which they are connected, as is apparent from the depths given below.
The Gulf of Mexico is from 5,000 to 7,000 feet in depth. The deepest part of the Caribbean Sea, on a line connecting Porto Rico and Costa Rica, averages 7,000 feet, and near the latter it reaches a depth of 14,000; but the ocean, immediately outside of the Lesser Antilles, is more than 18,000 feet deep.
The Mediterranean is divided into two basins, by a rocky isthmus, from 50 to 500 feet below the surface, lying between Sicily and Cape Bon, in Africa. The western basin is over 9,000 feet in depth, and comparatively uniform; while the eastern is more irregular, varying from 6,000 near the center, to 13,000 feet, south of the Ionian Islands. The Red Sea has an irregular bottom,with an average depth of 3,000 feet, but in some places it reaches 6,000.
The Baltic Sea, being a simple depression in the great European plain, is but a few hundred feet deep. In the North Sea, the depth averages 300 feet, and rarely exceeds 600. The continent is here prolonged in the form of a submarine plain, whose highest portions form the British Isles.
The Border Seas of Asia, lying within the chain of continental islands, are only a few hundred feet in depth, while immediately without those islands, abrupt slopes descend to the great depths of the Pacific basin.
Smaller inlets are also of frequent occurrence, especially in districts where mountain ranges approach the borders of the ocean. Such are thelochsof Scotland, thevoesof the Shetland Islands, and thefiordsof Norway and Greenland. The termlagoonis usually applied to lake-like inlets.
Salt and Other Ingredients of Sea-water.The waters of the ocean are salt, holding in solution various saline matters. The saline ingredients amount to rather more than thirty-five grains in a thousand grains of sea-water. The most abundant of these is chloride of sodium or common salt, which in general forms about a third of the whole. Besides this, sea-water contains some magnesia, lime, potash, and traces of iodine and bromine.
The following table exhibits the exact percentage composition of sea-water.
One hundred parts by weight of sea-water contain:
How the Sea gets its Color.The color of sea-water is due to the character of the skies and clouds above, and to vegetable and animal objects growing and living in it. The luminosity or phosphorescence of the ocean is due to the decay of animal and vegetable substances, but in some cases it arises from the presence of myriads of living animals, which, like the glow-worm and fire-fly of the land and air, have the power of emitting light.
Ocean Temperature.The water of the ocean appears generally to agree with that of the climate in which it is situated. In warm latitudes the temperature of the deep sea diminishes with the depth below the surface until a certain depth is reached, below which it appears to retain an equable temperature, this being about 40 degrees Fahrenheit. In the Polar Seas, where the temperature of the surface is lower than 40 degrees the heat increases downward until it reaches that point. In latitude 70° the temperature of the ocean is considered to be the same at all depths.
HOW TIDES ARE FORMED BY ACTION OF THE MOONThe moon pulls the waters of the earth into a great double wave heaping it up on the side nearest to the moon and on the opposite side. As the earth rotates, this double wave moves round the earth, and the crests and troughs alternately produce high and low tide. Thus there are two high and two low tides daily, at intervals of about twelve hours, or half a Sun or day.
HOW TIDES ARE FORMED BY ACTION OF THE MOON
The moon pulls the waters of the earth into a great double wave heaping it up on the side nearest to the moon and on the opposite side. As the earth rotates, this double wave moves round the earth, and the crests and troughs alternately produce high and low tide. Thus there are two high and two low tides daily, at intervals of about twelve hours, or half a Sun or day.
The waters of the ocean are retained in their bed by the attraction of gravitation. This power is great in proportion to the mass; and as the earth is of much greater mass than the particles of water on its surface, it attracts them and keeps them in their assigned places. But the sun and moon also possess this power of attraction, and notwithstanding their distance, attract and draw themup to a certain elevation. The vast mass of the waters being drawn up by the moon into a mountain or curve of water forms what is called the “great primary or tidal wave.”
VAST OCEAN CAVERN AT CAPRI, WIDELY KNOWN AS THE “BLUE GROTTO”This remarkable cavern, on the shore of the island of Capri, at the entrance of the Bay of Naples, is entered from the sea, and is one hundred and eighteen feet long and forty feet high, with a breadth of ninety-eight feet at its widest part. It derives its name from the wonderful blue reflection of the sun’s rays through the water, which gives the interior its marvelous beauty and majesty. The cavern has been created by the ceaseless action of the tide.
VAST OCEAN CAVERN AT CAPRI, WIDELY KNOWN AS THE “BLUE GROTTO”
This remarkable cavern, on the shore of the island of Capri, at the entrance of the Bay of Naples, is entered from the sea, and is one hundred and eighteen feet long and forty feet high, with a breadth of ninety-eight feet at its widest part. It derives its name from the wonderful blue reflection of the sun’s rays through the water, which gives the interior its marvelous beauty and majesty. The cavern has been created by the ceaseless action of the tide.
Ebb-tide and Flood-tide.This drawing up of the waters of mid-ocean causes a recession from the shores, thus giving rise to ebb-tide, or low water. But when the temporary attraction ceases the waters flow back to their natural level, returning to shore and forming flood-tide, or high water. This culmination or rising of the waters in the great tidal wave takes place twice in twenty-four hours and fifty minutes. The combined influence of the sun and moon at new and full moon augments the size of this wave, and causes the “spring-tides” at those periods.
Height of Tides.High water at the various points along the coast is dependent on the return of this great wave, though some variations are caused by local peculiarities; and the height of the tide also varies greatly in different parts of the earth.
On the eastern coast of North America, the average rise of the tide is from nine to twelve feet. At the entrance to the Bay of Fundy, however, it rises eighteen feet, while at the head of that bay it reaches sixty, and in the highest spring tides, even seventy feet. At Bristol, in England, the spring tides rise to forty feet; and at St. Malo, on the south coast of the English Channel, they reach fifty feet.
Differences in level, produced by high tides, cause currents which vary in force and direction with the condition of the tide, producing, in some cases, dangerous whirlpools. The famous Maelstrom, off the coast of Norway, is but a tidal current, which rushes with great violence between two of the Lofoden Islands, causing a whirling motion in the water which is reversed at each ebb and flow of the tide.
Such is, also, the famous whirlpool of Charybdis, in the Straight of Messina, and many others of less note. The powerful currents of Hell Gate, in thepassage from Long Island Sound to New York Bay, are due to a similar cause, high water occurring at different hours in the bay and in the west end of the sound.
The waves of the ocean, which are caused by the action of the wind, and which are called secondary or wind waves are of a totally different character from the tidal wave. The influence of the wind is supposed not to extend to a greater depth than forty or fifty feet, the deep sea, though raised in a great mass by the grand tidal movement, being free from agitation. Wind waves at a distance from the shore are comparatively low and long, but in shoal water they assume a greater curvature, and fall on the beach either in gentle ripples or in mighty breakers, according to the depth of the water and the force of the wind. The heavy swell which occasionally takes place, called the “ground sea,” is supposed to originate in distant storms of wind.
Currents in the ocean arise from various causes. They may be produced by long-continued gales of wind, by the melting of polar ice, or by any cause that may give rise to onward movements of limited portions of the great mass of waters. Other currents, and of these only is it necessary to speak in this connection, are permanent. The most remarkable of these are the polar currents and the equatorial currents.
Polar Currentsare produced by the perpetual movement of the waters from the poles to the equator. In accordance with the laws of mechanics, an accumulation of the waters takes place on that part of the globe which has the greatest velocity of motion; and as the earth in turning on its axis moves with far greater velocity at the equator, the waters continually flow toward that line from the poles.
Equatorial Currents.This accumulation of the waters at the equator tends to produce the equatorial currents, which consist of the continuous progression of the tropical seas in a westerly direction. When the wave brought by the polar currents arrives—coming as it does from regions where it naturally has less velocity—it does not at once acquire the velocity of the earth’s motion at the equator; and since the rotation of the earth is from west to east, this portion of the water lagging behind forms a stream or current which has an apparent motion from east to west, that is to say, apparent as regards the earth, but real in relation to the adjacent land and water. The trade winds, which in this zone blow constantly in the same direction, lend their aid in maintaining the equatorial current.
An extensive system of currents appears to arise in the Antarctic Ocean. A current of cold water flowing northward joins the equatorial current in the Pacific. Entering the Indian Ocean, it maintains its westerly course until it approaches the shores of Africa; then bending southward it rushes through the Mozambique Channel, and doubling the Cape of Good Hope travels northward until it arrives at the Bight of Benin. This current then joins the equatorial current, and crossing the Atlantic from the coast of Guinea to that of Brazil, it is divided into two branches by the projecting headland of Cape San Roque, one flowing southward and the other northward.
The Gulf Stream.After passing the Island of Trinidad, this great oceanic current enters the Gulf of Mexico, and there acquires a high temperature, and sweeping round that sea it again pours forth into the Atlantic, forming the most powerful of known currents, called the Gulf Stream. Issuing from the Gulf of Mexico, this current of warm water rushes with considerable force through the Bahama Channel; then taking a northerly course it travels along the eastern shores of North America, and at Newfoundland is turned to the eastward by an opposing cold current which sets in from Baffin’s Bay. It now maintains an easterly direction, and crossing the Atlantic arrives at the Azores in about twenty-eight days, and divides its waters on the coast of France and Spain: one portion goes southward and at length joins the grand current which sets from the coast of Guinea; and another portion travels northward and skirts the western coasts of Europe. These currents are seldom more than 500 feet deep.
The atmosphere is the vast ocean of air that envelops the earth and makes life possible on our globe. It absorbs the heat and vapors caused by the action of the sun upon the surface of both land and water, and is the medium through which the ever-changing phenomena ofclimateandweatherare produced. The two great forces of nature acting in connection with it aregravitationandheat, or solar radiation; and the results of their ceaseless action may be summed up as follows: (1)Temperature, or heat, which we soon learn to know by our senses, and to measure by the thermometer. (2)Evaporation, which changes the weight of the air by carrying invisible moisture through it. This change ofweightis indicated by the barometer. (3)Condensation, producing fog, dew, rain, hail, and snow; all estimated accurately by the rain gauge or pluviometer. (4)Motions, as in the winds, varying from the gentle breeze to the awful cyclone, the force and velocity of which are indicated by the anemometer. (5)Electricity, producing lightning, thunder, magnetic and chemical changes in the atmosphere. (6)Optical Phenomena, such as rainbows, haloes, coronas, mirage, and the auroras.
The Earth is enveloped in its own atmosphere, which like a transparent covering surrounds it, and revolves with it. This atmosphere does not extend to more than forty or fifty miles above the earth’s surface, and is higher at the equator than at the poles.