snow-covered Alps and the elevated temperature of the Medi

terranean.

336. The bora, a northeast wind, so called in Istria and Dalmatia, is sometimes so furious as to overturn horses at plow. The mistral and the vent de bise are winds which prevail in the southeast of France. The mistral blows from the northwest, descending from the mountains of central France, and sweeping over the ancient provinces of Provence and Languedoc, where it is supposed to contribute greatly to the salubrity of the air by dispelling the exhalations from the marshes and stagnant waters common in that region of extensive levels. It is very fearful in the Gulf of Lyons; hence the name of that gulf, not derived, as commonly imagined, from the city of Lyons, but from the lion-like violence of its tempests. The vent de bise (black wind) is a cold, piercing current from the Alps and the mountains of Auvergne, which chiefly follows the course of the Rhone, in the valley through which it runs, rendering the climate in winter very severe. In Spain, a north wind, called the gallego, is of a very formidable character. 397. Hot and dry winds are very frequent in countries contiguous to the tropical regions. Large deserts and plains, covered with little vegetation, engender very warm winds; these winds, which are of a noxious character, prevail in the vast deserts of Asia and Africa, where they show themselves in all their force. Nubia, Arabia, Persia, and other parts of Asia, are visited by a scorching wind peculiar to the desert. In Arabia it is called samoun, from the Arabic samma, which signifies hot and poisonous. It is also named samiel, from samm, poison. In Egypt it is called chamsin (fifty) because it blows for fifty days, from the end of April until June, at the commencement of the inundation of the Nile. In the western part of the Sahara it is named harmattan.

398. The simoon is announced by the troubled appearance of the horizon; afterward the sky becomes obscured, and the sun loses its brilliancy,-paler than the moon, its light no longer projects a shadow; the green of the trees appears of a dirty blue, the birds are restless, and the affrighted animals wander in all directions. The rapid evaporation occurring at the surface of the human body dries the skin, inflames the throat, accelerates respiration, and causes a violent thirst. The water contained in the skins evaporates, and the caravan is a prey to all the horrors of thirst.

399. This hot wind is deleterious in its mildest forms, occasionally destructive, and many a pilgrim to the shrine of the prophet at Mecra, and merchant to the marts of Bagdad, have perished by its noxious, suffocating influences. Bruce suffered from it when ascending the Nile, he and his company becoming so enervated as to be incapable of pitching their tents, oppressed as well by an intolerable headache. "The poisonous simoon," he remarks, when at Chendi, "blew as if it came from an oven; our eyes were dim, our lips cracked, our knees tottering, our throats perfectly dry; and no relief was found from drinking an immoderate quantity of water:"

64

400. In June, 1813," says Buckhardt, "in going from Siout to Esné, I was surprised by the simoon in the plain which separates Furschiout from Berdys. When the wind arose I was alone, mounted on my dromedary, and at a distance from every tree and habitation. I endeavored to protect my face by wrapping it in a handkerchief. Meanwhile the dromedary, into whose eyes the wind drove the sand, became restless, commenced galloping, and caused me to lose the stirrups. I remained lying on the earth without moving from the spot, for I could not see to a distance of ten metres, and I wrapped myself up in my clothes until the wind had abated. I then went in search after my dromedary, which I found at a very great

Questions-306. What is said of the bora? The mistral? The vent de bise? 397. Where are hot winds very frequent? By what name is the burning wind called in Arabia? By what other name is it known? What is it called in Egypt, and why? In the western part of Sahara? 898. How is the simoon announced? How does it affect the human body? 899. What further is remarked respecting this hot wind? How did Bruce suffer from it?

name of poisonous winds; or, more correctly, hot winds of the desert. Such, in fact, is their quality; and their heat is sometimes so excessive that it is difficult to form an idea of their violence without having experienced it; but it may be compared to the heat of a large oven at the moment of drawing out the bread. When these winds begin to blow, the atmosphere assumes an alarming aspect. The sky, at other times so clear in this climate, becomes dark and heavy; the sun loses its splendor, and appears of a violet color. The air is not cloudy, but gray and thick; and is in fact with an extremely subtile dust, that penetrates everywhere.

402. "This wind, always light and rapid, is not at first extremely hot, but it increases in heat in proportion as it continues. All animated bodies soon discover it by the change it produces in them. The lungs, which a too rarefied air no longer expands, are contracted and become painful. Respiration is short and difficult, the skin parched and dry, and the body consumed by an internal heat. In vain is recourse had to large drafts of water; nothing can restore perspiration. In vain is coolness sought for; all bodies in which it is usual to find it deceive the hand that touches them. Marble, iron, water, notwithstanding the sun no longer appears, are hot. The streets are deserted, and the dead silence of night reigns everywhere. The inhabitants of towns and villages shut themselves up in their houses-and those of the deserts in their tents, or in pits they dig in the earth-where they wait the termination of this destructive heat. 403. It usually lasts three days, but if it exceeds that time it becomes insupportable. Woe to the traveler whom this wind surprises remote from shelter he must suffer all its dreadful consequences, which sometimes are mortal. The danger is most imminent when it blows in squalls, for then the rapidity of the wind increases the heat to such a degree as to cause sudden death. This death is a real suffocation; the lungs, being empty, are convulsed; the circulation disordered, and the whole mass of blood, driven by the heat toward the head and breast; whence that hemorrhage at the nose and mouth which happens after death.

404.This wind is especially fatal to persons of a plethoric habit, and those in whom fatigue has destroyed the tone of the muscles and vessels. The corpse remains a long time warm, swells, turns blue, and is easily sep arated; all of which are signs of that putrid fermentation which takes place when the humors become stagnant. These accidents are to be avoided by stopping the nose and mouth with handkerchiefs; an efficacious method is also that practiced by the camels, who bury their noses in the sand, and keep them there till the squall is over.

405. "Another quality of this wind is the extreme aridity, which is such that water sprinkled upon the floor evaporates in a few minutes. By this extreme dryness it withers and strips all the plants, and by exhaling too

Questions.-What does he say of it? 400. Mention some of the particulars related by Buckhardt. To what does 401. What does Volney say respecting these winds? he compare their heat? What is the aspect of the atmosphere during the continuance of the simoon? 402. What changes does it produce on all animate bodies? 408. How long does it usually last? When is the danger most imminent? 404. To whom is the wind especially fatal? 405. What other quality does this wind possess? Give particulars.

suddenly the emanations from animal bodies, crisps the skin, closes the pores, and causes that fevciish heat which is the invariable effect of suppressed perspiration."

406. The Harmattan blows from the northeast, over Senegambia and Guinea, to that part of the coast of Africa lying between Cape Verde, in 15° north latitude, to Cape Lopez, in 1° south latitude, a coast line of upward of two thousand miles. It occurs during December, January, and February, generally three or four times during that season. It comes on at any hour of the day, at any time of the tide, or at any period of the moon, continuing sometimes only a day or two, at other times five or six days, and it has been known to last upward of a fortnight.

407. Extreme dryness is the property of this wind; all vegetation droops and withers, and should the harmattan blow for several days, the leaves of the lemon, orange, and lime-trees become so parched that they may be readily rubbed into dust. Even household furniture cracks, and in many instances flies to pieces. Though this wind is so pernicious in its effects upon vegetable life, yet it is conducive to the health of the human species, by removing dampness from the atmosphere, and counteracting its effects after a long rainy season.

408. The Sirocco is a hot southeast wind, prevailing in the Mediterranean, in Italy, and Sicily, but felt most violently in the country around Naples, and at Palermo. It sometimes It sometimes commences about the time of the summer solstice, but blows occasionally with great force in the month of July. Though usually attributed to the Sahara, it is supposed by some to arise on the arid rocks of Sicily; and hence is far more violent on the north than on the south coast of the island, about Palermo, and also in the neighborhood of Naples.

409. It is thus described by a traveler during his stay at Palermo :

"On Sunday, July 8th, we had the long-expected sirocco wind, which, although our expectations had been raised pretty high, yet I own greatly exceeded them. Friday and Saturday were uncommonly cool, the mercury never being higher than 7210; and although the sirocco is said to have set in early on Sunday morning, the air in our apartments, which are very large, with high ceilings, was not in the least affected by it at eight o'clock, when I rose. I opened the door without having any suspicion of such a change; and indeed I never was more astonished in my life. The first blast of it on my face felt like the burning steam from the mouth of an oven. I drew back my head and shut the door, calling out to Fullarton that the whole atmosphere was in a flame. However, we ventured to open another door that leads to a cool platform, where we usually walk; this was not exposed to the wind; and here I found the heat much more supportable than I could have expected from the first specimen I had of it at the other door. It felt somewhat like the subterranean sweating-stoves at Naples. but still much hotter. In a few minutes we found every fiber greatly relaxed, and the pores opened to such a degree, that we expected soon to be thrown into a profuse sweat.

410. "I went to examine the thermometer, and found the air in the room as yet so little affected that it stood only at 730. The preceding night it was at 7240. I took it out to the open air, when it immediately rose to 110°, and soon after to 1120; and I am confident that in our old lodgings, or anywhere within the city, it must have risen several degrees higher. The air was thick and heavy, but the barometer was little affected: it had fallen

only about a line. The sun did not once appear the whole day, otherwise I am persuaded the heat must have been insupportable; on that side of our platform which is exposed to the wind, it was with difficulty we could bear

it for a few minutes. Here I exposed a little pomatum, which was melted down as if I had laid it before the fire. I attempted to take a walk in the street to see if any creature was stirring, but I found it too much for me, and was glad to get up stairs again. This extraordinary heat continued till three o'clock in the afternoon, when the wind changed at once almost to the opposite point of the compass. All nature languishes under the influence of this wind; vegetation droops and withers; the Italians suffering from it not less than strangers. When any feeble literary production appears, the strongest phrase of disapprobation they can bestow is, 'It was written in the time of the sirocco.'"

411. The deserts of Asia and Africa are the regions in which the hot or scorching winds prevail; but in Spain the Salano, a wind which is supposed to arise on the plains of Andalusia, throws the majority of individuals into a condition of peculiar languor. In India, which is covered with a rich vegetation, and in Chile, in Louisiana, and in the great level plains (Llanos) of the Orinoco, there are certain local winds of a very elevated temperature.

LESSON IV.

PERMANENT WINDS.

412. THE Trade-winds are those permanent breezes which prevail within the tropics, and which maintain nearly the same direction and rate throughout the year. Their direction is from the northeast in the northern hemisphere, and from the southeast south of the line; but it is more decidedly from the east as the equator is approached. They extend generally from about 28° to 30° on each side of the equator, but their limits vary considerably as the sun is north or south of the equator; their external and internal boundaries are also very different in the Atlantic and Indian oceans. It is only over the wide ocean that the trade-winds can blow uninterruptedly. Between them

a colder atmosphere moves to supply its place. Thus two currents are created in each hemisphere, an upper and a lower, but flowing in opposite directions. If the earth did not rotate on its axis, the lower current in the northern hemisphere, or the trade-wind, would be from north to south, and in the southern hemisphere from south to north. The earth, however, rotates from west to east, and the atmosphere surrounding it partakes of this rotary motion; hence these winds become northeast and southeast.

414. The movements of the trade-winds, and the laws by which they are governed, are thus explained by a well-known writer :

"From the parallel of about 30° north and south, nearly to the equator, we have two zones of perpetual winds, viz. the zone of northeast trades on this side, and of southeast on that. They blow perpetually, and are as steady and as constant as the currents of the Mississippi River—always moving in the same direction. As these two currents of air are constantly flowing from the poles toward the equator, we are safe in assuming that the air which they keep in motion must return by some channel to the place near the poles, whence it came in order to supply the trades. If this were not so, these winds would soon exhaust the polar regions of atmosphere, and pile it up about the equator, and then cease to blow for the want of air to make more wind of.

415. "This return current, therefore, must be in the upper regions of the atmosphere, at least until it passes over those parallels between which the trade-winds are always blowing on the surface. The return current must also move in the direction opposite to the direction of that wind which it is intended to supply. These direct and counter-currents are also made to move in a sort of spiral curve, turning to the west as they go from the poles to the equator, and in the opposite direction as they move from the equator toward the poles.

416. "This turning is caused by the rotation of the earth on its axis. The earth, we know, moves from west to east. Now if we imagine a particle of atmosphere at the north pole, where it is at rest, to be put in motion in a straight line toward the equator, we can easily see how this particle of air, coming from the pole, where it did not partake of the diurnal motion of the earth, would, in consequence of its vis inertia, find, as it travels south, the earth slipping under it, as it were, and thus it would appear to be coming from the northeast and going toward the southwest: in other words, it would be a northeast wind.

417. “On the other hand, we can perceive how a like particle of atmosphere that starts from the equator, to take the place of the other at the pole, would, as it travels north, in consequence of its vis inertia, be going toward the east faster than the earth. It would therefore appear to be blowing from the southwest, and going toward the northeast, and exactly in the opposite direction to the other. Writing south for north, the same takes place between the south pole and the equator. Now this is the process which is exactly going on in Nature; and if we take the motions of these two particles as the type of the motion of all, we shall have an illustration of the great currents in the air, the equator being near one of the nodes, and there being two systems of currents-an upper and an underbetween it and each pole.

418. "Let us return now to our northern particle, and follow it in a round from the north pole to the equator and back again, supposing it, for the present, to turn back toward the pole after reaching the equator. Setting off from the polar regions, this particle of air, for some reason which does not appear to have been satisfactorily explained by philosophers, travels in the upper regions of the atmosphere, until it gets near the parallel of 30°. Here it meets, also in the clouds, the hypothetical particle that is going from the equator to take its place toward the pole.

419. "About this parallel of 30°, then, these two particles meet, press

Questions.-414. Where have we two zones of perpetual winds? What are we safe in assuming? Why? 415. Where must this return current be? Which way do the direct and counter-currents turn? 416. How is this turning caused? Explain. 417. Explain the direction of the return current. 418. Describe the course of a particle of atmosphere proceeding from the polar regions toward the equator. What does it meet near the parallel of 800 ? 419. What results foliow? What surface currents are here ejected? 420. From what part of the calm region do these winds come, and what consequently may be inferred?

* NODES, the point where the ascending and descending currents cross each other.

against each other with the whole amount of their motive power, produce a calm and an accumulation of atmosphere sufficient to balance the pressure from the two winds north and south. From under this bank of calms two surface currents of wind are ejected; one toward the equator, as the northeast trades--the other toward the poles, as the southwest passage winds— supposing that we are now considering what takes place in the northern heinisphere only.

420. "These winds come out at the lower surface of the calm region, and consequently the place of the air borne away in this manner must be supplied, we may infer by downward currents from the superincumbent air of the calm region. Like the case of a vessel of water which has two streams from opposite directions running in at the top and two of equal capacity discharging in opposite directions at the bottom-the motion of the water in the vessel would be downward so is the motion of air in this calm The barometer, in this calm region, is said by Humboldt and others to stand higher than it does either to the north or to the south of it; and this is another proof as to the banking up here of the atmosphere and pressure from its downward motion.

zone.

421. "Following our imaginary particle of air from the north across this calm belt, we now feel it moving on the surface of the earth as the northeast trade-wind, and as such it continues till it arrives near the equator, where it meets a like hypothetical particle, which has blown as the southwest trade-wind." [The writer here proceeds upon the supposition that the air from the polar region descending at the calm belt uniformly passes to its equatorial side, and so enters the trade-wind region. It is proper to observe, however, that among a majority of scientific men the evidence that this is the case is deemed inconclusive; although the probability that such is its frequent course is by no means disproved.] "Here, at this equatorial place of meeting, there is another conflict of winds, and another calm region, for a northeast and southeast wind can not blow at the same time in the same place. The two particles have been put in motion by the same power; they meet with equal force, and therefore, at their place of meeting, are stopped in their course. Here, therefore, there is also

a calm belt.

422. Warmed by the heat of the sun, and pressed on each side by the whole force of the northeast and southeast trades, these two hypothetical particles, taken as the type of the whole, ascend. This operation is the reverse of that which took place at the other meeting near the parallel of 30o. This imaginary particle now returns to the upper regions of the atmosphere again, and travels there until it meets, near the calm belt of Cancer, its fellow-particle from the north, where it descends as before, and continues to flow toward the pole as a surface wind from the southwest." [Here, again, the writer proceeds upon the supposition that the descending particle of air crosses the calm belt, and continues its course on the opposite side—a theory regarded as resting upon an uncertain basis.

423. The general circulation of the atmosphere which manifests itself thus uniformly in the torrid regions and with less constancy in the temperate, has been a subject of profound scientific investigation. The laws which govern it are complex and obscure; but it is believed that the daily increasing observations, especially those in the higher latitudes, will throw light upon the subject, and in process of time will unravel its most perplexing mysteries.

424. Nothing excited the wonder of the early navigators so much as the trade-winds which blow regularly within the tropics. The companions of Columbus were terrified when they found themselves driven on by continuous easterly breezes, which seemed to forewarn them that they would never return to their country. Fortunately for the fame of the great navigator, and for the world, he firmly held on his course, and made the discovery of a new continent.

425. The trade-winds serve important uses to navigators, in facilitating the passage of ships round the world. In passing from the Canaries to Cumana, on the north coast of South America, it is scarcely ever necessary

Questions.-Illustrate the downward motion of the air in this calm zone. What is another proof of the banking up here of the atmosphere and pressure from its downward motion? 421. Where is the particle of air supposed to move after leaving the calm belt? What occurs at the equatorial place of meeting? 422. Why does it here ascend? Describe its track as it returns toward the pole. 423. Investigation of the general circulation of the atmosphere? Laws which govern it, and prospect of a future explanation of the subject? 424. Wonder of the early navigators? The companions of Columbus ? 425. Uses of the trade-winds? Illustrate. Route of an outward and return voyage from New York to Canton

to touch the sails of a ship; and with equal facility a passage is made across the Pacific, from Acapulco, on the west coast of Mexico, to the Philippine Islands. The customary route of vessels on their outward voyage from New York to Canton is by the way of Cape Horn, and thence westwardly through the Pacific: the return voyage is by the way of the Cape of Good Hope. If a channel were cut through the Isthmus of Panama, the voyage to China

CAPE HORN.

would be more speedy, agreeable, and safe than the usual route by Cape Horn.

426. All mariners and passengers have spoken with delight of the region of the trade-winds. It is noted for the favoring gales, the transparent atmosphere, the splendid sunsets, and the brilliancy of the unclouded heavens, day and night. Columbus, in recording his first voyage into their territory, compares the air, soft and refreshing without being cool, to that of the pure and balmy April mornings he had experienced in Andalusia. Humboldt, in describing the tropical regions, remarks upon the mildness of the climate and the beauty of the southern sky. He observed stars seen from infancy progressively sinking and finally disappearing below the horizon, an unknown firmament unfolding its aspect, and scattered nebulæ rivaling in splendor the milky way. The Spaniards gave to the zone in which the trade-winds are constant the title el Golpo de las Damas, the Sea of the Ladies, on account of the ease with which it may be navigated, the uniform temperature prevalent night and day, and its pacific aspect.

LESSON V.

PERIODICAL WINDS.

427. PERIODICAL winds are those which regularly prevail at a certain time of the year or of the day. The monsoons of the Indian Ocean, the Etesian winds of the Mediterranean, and the land and sea breezes, are of this class.

428. Monsoons, from the Malay word moussin, signifying แ a season," are regular periodical winds which sweep over the Indian Ocean and the whole of Hindoostan, changing their direction after an interval of about six months, as the sun moves into the northern or southern hemispheres; hence the term season winds, or monsoons. These winds are a modification of the trade-winds, occasioned by the position of the sun in different seasons, the openings in the chain of islands separating the Indian Ocean from the Pacific, the interposition of the Asiatic continent, and the rarefied atmosphere of Africa and Australia.

429. From 3° south of the equator to the northern shores of the Indian Ocean, including the Arabian Sea, the Bay of Bengal, and the Chinese Sea, a southwest wind prevails during most of the season, from April to October, after which a northeast wind sets in, and prevails through most of the remaining half of the year, from October to April. While the wind north of the equator is southwest, a southeast wind prevails between

Questions-426. For what is the region of the trade-winds noted? 427. What are periodical winds? Name those which belong to this class. 42. What are monsoons ? From what is the term derived? What is said of these winds? 429. What are the limits of the region having a southwest wind from April to October?

3° and 10° south of the line; and when the wind north of the equator is northeast, that south of it is northwest.

430. The western boundary of the region of the monsoons is the African shore; its eastern limit is supposed to be about the meridian of 150° east longitude; its northern confine is near the parallel of 27° north latitude; its southern extremity has been already stated. The monsoons are much stronger than the trade-winds, and may be called gales; they sometimes blow with such violence that ships are obliged to reef their sails. They are not confined to the ocean, but extend over the whole of Hindoostan to the Himalaya Mountains.

431. Mr. Caunter, a resident of Madras, gives the following interesting account of a storm which occurred there during the shifting of theso winds :

'On the 15th of October the flag-staff was struck, as a signal for all vessels to leave the roads, lest they should be overtaken by the monsoon. On that very morning some premonitory symptoms of the approaching war of elements had appeared. As the house we occupied overlooked the beach, we could behold the setting in of the monsoon in all its grand and terrific sublimity. The wind, with a force which nothing could resist, bent the tufted heads of the tall, slim cocoa-nut trees almost to the earth, flinging the light sand into the air in eddying vortices, until the rain had either so increased its gravity or beaten it into a mass, as to prevent the wind from raising it.

432. "The pale lightning streamed from the clouds in broad sheets of flame, which appeared to encircle the heavens as if every element had been converted into fire, and the world was on the eve of a general confiagration; while the peal, which instantly followed, was like the explosion of a gunpowder magazine. The heavens seemed to be one vast reservoir of flame, which was propelled from its voluminous bed by some invisible but omnipotent agency, and threatened to fling its fiery ruin upon everything around. In some parts, however, of the pitchy vapor, by which the skies were by this time completely overspread, the lightning was seen only occasionally to glimmer in faint streaks of light, as if struggling, but unable, to escape from its prison-igniting, but too weak to burst, the impervious bosoms of those capacious magazines in which it was at once engendered and pent up.

433. "So heavy and continuous was the rain, that scarcely anything save those vivid bursts of light, which nothing could arrest or resist, was perceptible through it. The thunder was so painfully loud that it frequently caused the ear to throb; it seemed as if mines were momentarily springing in the heavens, and I could almost fancy that one of the sublimest fictions of heathen fable was realized at this moment before me, and that I was hearing an assault of the Titans. The surf was raised by the wind and scattered in thin billows of foam over the esplanade, which was completely powdered with the white, feathery spray. It extended several hundred yards from the beach; fish, upward of three inches long, were found upon the flat roofs of houses in the town during the prevalence of the monsoon-either blown from the sea by the violence of the gales, or taken up in the water-spouts, which are very prevalent in this tempest

uous season.

434. "When these burst, whatever they contain is frequently borne by the sweeping blast to a considerable distance over-land, and deposited in the most uncongenial situations; so that now, during the violence of these tropical storms, fish are found alive on the tops of houses; nor is this any longer a matter of surprise to the established resident in India, who sees every year a repetition of this singular phenomenon. During the extreme violence of the storm, the heat was occasionally almost beyond endurance, particularly after the first day or two, when the wind would at intervals entirely subside, so that not a breath of air could be felt, and the punka afforded but a partial relief to that distressing sensation which is caused by the oppressive stillness of the air so well known in India."

435. The monsoons are of great assistance to commerce; by

Questions. What wind prevails in this region from October to April? Describe the winds which prevail at different seasons between 80 and 100 south of the line. 480. What is the western boundary of the region of monsoons? Its eastern limit? Its northern? Its southern? Intensity of the monsoons? 485. Uses of monsoons ? .