breadth is about 400 miles, and it extends along the base of the Rocky Mountains as far as we have any acquaintance with that range. That portion of it which is traversed by the Platte river has, it is said, a strong resemblance to the barren steppes of Asia. The soil and rocks are saline, and incrustations of salt often appear on the surface, and the plants are such as are usually found in saline tracts. Trees and forests are almost unknown. This waste is scorched in summer by the rays of the sun, and chilled in winter by freezing winds from the mountains.

The SAVANNAHS and PRAIRIES are generally covered with a species of coarse grass, which often grows to the height of a man. They are numerous in the states which border on the Ohio and Mississippi rivers, particularly between the latter river and the Rocky Mountains; and in the western part of the state of New York, several prairies of small extent occur. And on the sea-coast of the United States, particularly in New Jersey, Maryland, the Carolinas, and Georgia, there are extensive plains in which scarcely anything grows, except stunted pines. These sterile and dreary tracts are called PINE BARRENS. The other vast plains in America, are the basins of the Amazon, the La Plata, and the Orinoco. In these plains extensive savannals occur. In the rainy season they are clothed with vegetation and verdure, but in times of drought they assume the appearance of deserts. In the lower part of the basin of the Amazon, they are called selvas or forest-plains; in Venezuela, LLANOS; and in Buenos Ayres, FAMPAS. The llanos of Venezuela extend 200 leagues along the Orinoco river, from its mouth to the foot of the Andes; and the pampas of Buenos Ayres stretch out to an immense extent between the Paraguay river and the Andes. Immense herds of wild cattle range over those

boundless plains.

a The savannahs and prairies, particularly about the Rocky Mountains, abound with herds of bisons, &c.

b There is something awful, but sad and gloomy, in the uniform aspect of these steppes (of Venezuela). Every thing seems motionless. The plains all around us seem to ascend towards the sky; and the vast and profound solitude appeared to our eyes like an ocean covered with verdure. The first aspect of the llanos excites scarcely less astonishment than the lofty peaks of the Andes.-HUMBOLDT.

e In 1548, Cristoval Rodriguez first let loose horned cattle on these extensive plains; and since that period, they have increased to a wonderful extent.

QUESTIONS FOR EXAMINATION ON CHAP. VIII.

18. Can

Pages 141-144.-What is meant by a plain? 2. Plains are either? 3. What specimens in this country of barren or uncultivated plains? 4. Where are we to expect the largest plains? 5. Can you describe the great plain which extends over the north and north-east of Europe? 6. Has it no elevations? 7. The height of the Valdai Hills? 8. Can you describe the steppes of Russia? 9. The puszta of Hungary? 10. Where are the Pontine Marshes? 11. The meaning of the terms Netherlands and Holland? 12. What is the extent of the great plain of Hungary? 13. The meaning of the term desert? 14. Are there any in Europe? 15. Why not? 16. The largest and most remarkable in the world? 17. The meaning of the term Sahara? you give a general description of it? 19. The oases? 20. To what did the ancients compare them? 21. The dangers and difficulties in crossing the Sahara? 22. What are the camels called? 23. Why are travellers obliged to direct their course by the stars or by the compass? 24. Can you give an instance of the calamities which occur in crossing the Sahara? 25. Why need we not describe the deserts of Arabia, Syria, and Persia? 26. The extent of the Great Salt Desert in Persia? 27. Where are the deserts in Hindostan, and what is said of them? 28. The Great Desert of Asia? 29. The Shamo? 30. The extent of the desert of Gobi? 31. Of the Shamo? 32. How does the Shamo differ from the saharas of Africa and Arabia? 33. Where is the great American Desert? 34. Its extent and character? 35. The savannahs and prairies are generally covered with? 36. Where are they most numerous? 37. Can you describe the great plains in America? 38. The llanos? 39. The pampas? 40. The savannahs and prairies 41. Pine barrens? 42. Selvas? 43. What description does Humboldt give of the llanos of Venezuela? 44. Are the wild cattle spoken of as indigenous ?

CHAPTER IX.

RIVERS AND LAKES.

RIVERS, as was shown in chapter seven, have their origin in mountainous and elevated regions.

The magnitude and character of rivers, generally speaking, depend upon the elevation of the mountains from which they derive their source, and the extent and nature of the country drained by them and their tributaries. This will be evident, if we look at the BASINS, or extent of country drained by the American and other great rivers, as represented on globes and maps. The extent of country drained by the Amazon and its affluents, is nearly equal to two

Some rivers are at once formed by the overflowing of lakes. b Nature of the country-that is, according to the humidity of the soil and climate.

K

thirds of the whole continent of Europe; and the basins of the Mississippi and La Plata are also of vast extent, though neither of them amounts to half the magnitude of the basin of the Amazon. It is almost unnecessary to observe, that the mountain-ranges from which the great rivers of America derive their sources, are the most extensive, and among the most elevated in the world. In the Old World also, it will be found that the great rivers have their origin in the principal mountain-ranges.

The velocity of rivers is, generally speaking, in proportion to the declivity of the ground over which they flow. When they meet with sudden declivities, RAPIDS are formed; when with abrupt or precipitous descents, CASCADES and

CATARACTS.

The velocity of rivers is also accelerated by the quantity or volume of the water which they convey. Hence, the deeper a river is in proportion to its breadth, the quicker is its motion; for the greater will be the pressure of the particles of water from behind, upon those that precede. When a river has acquired a momentum from passing over the steep declivities of its earlier course, it can travel during the latter part of its course with uniform velocity on slopes of very small inclination. Thus the Amazon, for the last 200 leagues of its course, has a descent of only 10 feet. that is th part of an inch for every 1,000 feet of that distance. And the Paraguay, for a considerable part of its course, descends only rd of an inch in a mile.

Most of the large rivers discharge their waters into the sea by several mouths; as the Nile, the Ganges, the Volga, the Niger, the Orinoco, and the Rhine. Some have only one mouth, as the La Plata, and the St. Lawrence. The mouth or estuary of the La Plata is 150 miles wide!

Some rivers are subject to periodical floods; as the Nile, the Ganges, the Indus, and the Mississippi. Those floods are produced by the heavy rains which fall during the wet season, particularly in the torrid zone, and by the annual melting of the snow on the mountains from which the rivers derive their sources. The annual overflow of the Nile was considered a mystery by the ancients, because, in Egypt, no rain ever falls. But-"Nature well known, no prodigies remain," the periodical overflow of the Nile is no longer considered a mystery.

The floods of rivers, particularly in the torrid zone, are often most destructive to life and property. The great flood of the Ganges, in 1822, destroyed, it was estimated, from 50,000 to 100,000 persons, and swept away several entire villages. At the same time, these floods serve to irrigate and fertilize soils, which would otherwise be sterile and unproductive, by spreading over them deposits of vegetable mud and slime. It is thus that Egypt is rescued by its noble river from the sands of the Lybian desert; * and to the gladdening and happy effects produced by its floods, the ancient Euphrates is indebted for its name."

a

CLASSIFICATION OF RIVERS.

The principal rivers in the world may be divided into TEN CLASSES, according to their lengths, as in the following table:

First Class.-Rivers between 4,000 and 3,000 miles long; as the Amazon, 3,900; the Mississippi with the Missouri, 4,000; the Yangtse-kiang, 3,000; the Nile, 3,000.

Second Class.-Rivers between 3,000 and 2,000 miles long; as the Yenessei, 2,900; the Hoang-ho, 2,600; the Obi, 2,500; the Lena, 2,400; the Niger or Quorra, 2,300; the Parana with the Paraguay, 2,300; the Amur or Saghalien, 2,300; the Volga, 2,200; the Mackenzie, (including the Athabasca, &c.), 2,200; the St. Lawrence (from Lake Superior), 2,000; the May-kuang or Mekon (in Cambodia), 2,000; the Arkansas, 2,000.

Third Class.-Rivers between 2,000 and 1,500 miles long; as the Indus, the Euphrates, and the Danube, about 1,700 each; the Ganges, the Brahmapootra, the San Francisco, the Araguay with the Tocantins, and the Irrawadi, about 1,500 each.

Fourth Class.-Rivers between 1,500 and 1,200 miles long; as

"The Nile, which marks the extent of fertility by the measure of its inundations."-GIBBON.

b

» Euphrates.—From a Greek word, which signifies to muke gled

"Sparsus in agros,

Fertilis Euphrates, Phariæ vice fungitur unda."-LUCAN

The authorities are no more agreed about the lengths of rivers than they are about the heights of mountains. Nor is it to be expected that they should; for the sources of many of them are still unknown. Except for the European rivers, the lengths given are, for the most part, mere estimates. The learner should be required to trace these rivers on the maps of the countries through which they flow, from their mouths to their sources, noting their tributaries, the towns built upon them, &c.

the Rio del Norte, 1,400; the Orinoco, the Dnieper, the Murray (in Australia), and the Amoo or Jihon, about 1,200 each.

Fifth Class.-Rivers between 1,200 and 1,000 miles long; as the Tigris, 1,140; the Don, 1,100; the Gareep or Orange River; the Sutlej, and the Syr or Sihon, about 1,000 each.

Sixth Class.-Rivers between 1,000 and 800 miles long; as the Magdalena, 860; the Colorado or Mendoza, 850; the Negro (between La Plata and Patagonia), the Uruguay, and the Godavery, about 800 each.

Seventh Class.-Rivers between 800 and 600 miles long; as the Rhine and the Northern Dwina, 760 each; the Oregon or Columbia, 750; the Dniester, 700; the Elbe, 690; the Gambia, 650; the Vistula, 630.

Eighth Class.-Rivers between 600 and 400 miles long; as the Loire, 570: the Oder, the Southern Dwina, and the Meuse, 550 each; the Tagus, 510; the Douro, 460; the Po, the Guadiana, and the Susquehanna, 450 each; the Seine, 430; the Ebro, 420; the Sacramento, 410; the Niemen, the Potomac, the Savannah, the Connecticut, 400 each.

Ninth Class.-Rivers between 400 and 300 miles long; as the Weser, 380; the Garonne and the Essequibo, 350 each; the Hudson, 325; the Delaware, 300.

Tenth Class.-Rivers under 300 miles long; as the Guadalquiver,* 290; the Shannon, 224; the Thames, 215; the Tiber, 215; the Tay, 120; the Forth, 115; the Clyde, 100.

LAKES.

LAKES may be classed into FOUR distinct kinds. The FIRST class consists of those which neither receive nor give out streams of water. Lakes of this class are usually very small, and are supposed to be the craters of extinct vol

canoes.

The SECOND class consists of those which receive no running water, but which give out rivers or streams. Such lakes are formed and fed by springs and internal reservoirs.

The THIRD, and largest class of lakes, consists of those which both receive and give out rivers or streams of water, as the great American lakes; the lakes of Ladoga, Onega,

• Guadalquiver.-The ancient Boetis. The Arabs gave it this name, which means the great river; for so it must have appeared to them. In the arid plains of Arabia there are no rivers deserving the name; nor in Northern Africa, from which they passed over into Spain.

b Rivers not mentioned in the CLASSIFICATION will be given in connexion with the countries through which they flow.