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by checking the progress of some diseases, and effectually curing others.

The SIMOOм and SAMIEL are peculiar to the burning deserts of Africa and Arabia; and of all others are the most dreadful and desolating in their effects. The Samiel, which occurs in the deserts of Bagdad, not only produces instantaneous death, but so mortifies the limbs of the body that they easily come asunder. Camels seem to have an instinctive knowledge of its approach, which they indicate by making

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an unusual noise; and to avoid breathing it they thrust their noses into the sand; and it is in a similar way that travellers endeavour to escape its effects, namely, by throwing themselves down with their faces close to the ground, till it passes over, which is usually in a few minutes.

The ETESIAN WINDS are periodical winds which blow from the north and north-east for about six weeks throughout the Mediterranean, particularly the Levant. They commence about the middle of July, and blow only during the day, beginning about nine in the morning. These winds bring rain and fertility to the countries on the northern coast of Africa.

Near the north side of the equator, and between the respective trade-winds, there is a narrow belt, which is called the ZONE OF CALMS, because it is particularly subject to long-continued calms. It is however, occasionally visited by sudden and violent storms, particularly when the sun is vertical, or nearly so; and during this season, torrents of rain fall almost every day. The following description has been given of it:"The sun rises at six o'clock in a clear sky, and soon after midday, almost without exception, clouds appear, and a storm of rain and thunder follows. The sky then clears, and the sun sets at six o'clock without a cloud." Generally speaking, the zone of calms extends from the immediate neighbourhood of the equator to 5o or 6o north of it; but the breadth varies periodically. It is widest in September, and narrowest in January. Sailors dread the calms of this region more than they do the most violent storms."

The velocity of the wind varies from one to one hundred miles an hour. At the former its motion is almost imperceptible; at the latter it throws down houses, tears up trees by the roots, and sweeps their branches through the air. But in these countries the greatest velocity of the wind is supposed never to exceed sixty miles an hour. At ten miles an hour the wind is called a breeze; at twenty, a gale; at fifty, a storm; and a hurricane at eighty miles an hour.

QUESTIONS FOR EXAMINATION.

Pages 173-180.-The primary cause of wind? 2. The illustrations given? 3. How winds divided? 4. Trade-winds-why so called? 5. An instance of their utility to navigation? 6. Can you explain the cause of the trade-winds? 7. In what case would the trade-winds blow reguarly and constantly in the direction here stated? 8. Periodical winds 9 The monsoons? 10. Why so called? 11. Can you explain the cause of the monsoons? 12. When do they blow from the south-west! 13. When trom the north-east? 14. Why along the Gulf of Guinea, southerly and south-westerly winds constantly? 15. Why also on the coast of Peru? 16. Can you explain the land and sea breezes? 17. Where the winds, either permanent or periodical? 18. Where variable; and why? 19. What other winds are spoken of?

* See Coleridge's" Ancient Mariner," already referred to (p. 152): "Day after day, day after day,

Without a breath or motion;
As idle as a painted ship

Upon a painted ocean."

CHAPTER XIV.

DISTRIBUTION OF VEGETABLES.

VEGETABLES are adapted to every kind of climate, soil, and locality; and hence they are found in every part of the earth, from the equator to the polar regions.

Some vegetables delight in great heat, others in moderate, while others flourish best in cold. Some are confined to mountains, others to valleys, while others luxuriate in open plains. Some, again, require a moist soil and humid atmosphere, while others grow only in dry regions and arid tracts; and even on the surface of naked rocks, a species of vegetation exists. In this way, nearly the whole earth is covered with vegetation, and plants are found even in the dark recesses of caverns and mines, and in the beds of rivers, lakes, and seas. In short, heat and cold, sun and shade, dry and moist, fertile lands and pathless deserts, every locality and every temperature, has its own peculiar vegetation; and in those regions where vegetables cease to grow, lichens and mosses, capable of supporting animals, and even human beings, are found amid perpetual snows.

But it is in the torrid zone that vegetables are found in the greatest vigour, variety, and beauty. There, under the rays of a tropical sun, the herbaceous plants of the temperate and frigid zones, become shrubs-and shrubs, trees; while the size and number of the trees of those regions are beyond our conception.b

a It is in such situations the cow-tree is found; so called, from supplying the inhabitants of those parched regions with a rich vegetable milk. The following is Humboldt's description of it:-"On the barren flank of a rock grows a tree with coriaceous and dry leaves. Its large woody roots can scarcely penetrate into the stone. For several months in the year not a single shower moistens its foliage. Its branches appear dead and dried; but when the trunk is pierced, there flows from it a sweet and nourishing milk. It is at the rising of the sun that this vegetable fountain is most abundant. The blacks and natives are then seen hastening from all quarters, furnished with large bowls to receive the milk, which grows yellow and thickens at its surface."

The following description of the vegetation on the banks of the Cassiquiare, a river which connects the Amazon with the Orinoco, is from Humboldt:-"The luxuriousness of the vegetation increases in a manner of which it is difficult, even for those who are accustomed to

The trees of the majestic forests there are generally above a hundred feet in height; and many, particularly some species of the palm-tree, reach to 150, and even 200 feet. The gigantic baobab, on the banks of the Senegal, and in the islands of Cape Verd, is found with a trunk 50, 60, and even 70 feet in circumference, and many of its branches are larger than our largest trees. One of the leaves of the great fan-palm, will cover eight or ten men, and two or three of them are sufficient to cover a cottage.

The torrid zone is distinguished by the delicacy, as well as by the luxuriance of its vegetable productions. The most delicate spices, as cinnamon, nutmeg, cloves, and pepper, are confined to it; and in it are found the most delicious fruits, the most odoriferous herbs, and the most brilliant and beautiful flowers.

According to Humboldt, the species of plants known when he wrote, amounted to 44,000, of which 6,000 belonged to the class cryptogamia. They are thus distributed :-

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He also states the proportions of plants which grow in latitudes 0°, 45°, 68°, to be as the numbers 12, 4, and 1; which shows how prolific vegetation is in the equatorial parts of the earth, compared with the temperate and colder regions.

The utility of VEGETABLES to mankind is obvious. Some

the aspects of the forests between the tropics, to form an idea. There is no longer a beach: a palisade of tufted trees forms the bank of the river. You see a canal upwards of 400 yards broad, bordered by two enormous walls, clothed with lianas and foliage. We often tried to land, but without being able to step out of the boat. Toward sunset we sailed along the bank for an hour, to discover, not an opening (since none exists), but a spot less wooded, where our Indians, by means of the hatchet and manual labour, could give space enough for a restingplace for twelve or thirteen persons."

a Several have been discovered since, and more remain behind; for, except in Europe, the earth has been but partially explored.

Cryptogamia, such as have neither blossoms nor visible fructifications, as the mosses, ferns, &c.

supply us with food, as the different kinds of grain, fruits, and roots; others furnish us with clothing, as cotton, flax, and hemp. Some are valuable to us as medicines; and others supply us with timber, without which there could be neither commerce nor civilization.

Some valuable plants appear to be confined to their native soil, as the clove and nutmeg to the Spice Islands; the genuine cinnamon to Ceylon; and the best tea to China. But the seeds of the most useful plants have been carried over the earth in various ways, and propagated in soils and climates suitable to their nature.

Thus the seeds of plants and stones of fruits are carried by winds, currents, and birds, to different and often distant localities; and commercial intercourse brought the sugarcane and coffee-tree, natives of Asia, to the West Indies. The potato and Indian-corn are natives of America.

CHAPTER XV.

DISTRIBUTION OF ANIMALS.

THE earth, the air, the waters, and, in short, all nature appears to be full of animated beings. We cannot, however, take more than a hasty glance over this vast kingdom of

nature.

Like vegetables, ANIMALS are adapted to different climates, soils, and localities; and hence they are found in every part of the globe inhabited by man. The most useful animals, too, like the most important vegetables, are the most widely distributed. The ox, the horse, and the hog, are found from the equator to the polar circles; while the sheep, the goat, and the dog, extend over the whole habitable globe. Horses and oxen, indeed, degenerate and disappear as they approach the frigid zone, but their places are supplied by the existence of animals peculiarly adapted to those dreary regions. The uses of the reindeer to the Laplanders are well known, and animals of the same species abound in the Arctic regions of Asia and America. The dog, too, the affectionate and faithful follower of man in every country and in every clime, becomes doubly serviceable to him in those desolate regions

a The bread-fruit tree, the plantain and banana (which are varieties of the same species), the sago, and several other kinds of palm trees supply the inhabitants of the torrid zone with much of their food.

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