PART IV.

THE WINDS.

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F all the phenomena relating to astronomy, there is nothing more intricate, that has baffled the comprehension of philosophers, and is yet so little understood, as that of the Winds and their government.

The Trade Winds, in consequence of their uniform and undeviating courses, have been attempted to be accounted for, and which opinions have gained general belief, that they are caused by the rarefying power of the Sun on the atmospheric air, thereby forcing the Winds within the tropics to follow the Sun's path. But the Winds without the tropics, by reason of their unsteady adherence to any particular point of the compass for any certain time, have eluded altogether the researches of astronomers, and so far as information has been obtained, no one has ever attempted to point out any certain laws, whereby the Winds are regulated.

How the doctrine of rarefaction to account for the Trade Winds, has gained so many adherents, particularly from the learned, is really astonishing; because, ou a moment's reflection it will be evident, that this operation could not occasion the cousequences attendant on them.

The very extraordinary means that astronomers take to substantiate their principles, by perverting the powers differently in the same objects on different subjects, at various times, in order to suit their particular doctrines, are very remarkable. Do they think like the ostrich, who when hunted, hides his head, supposing thereby to blind his pursuers, because he will not see?

The different degrees of heat, have been

attributed on the different planets, according to the distances that they are situated from the Sun, but when it is found necessary to suppose the Earth to be further from the Sun in our summer than it is in winter, so much as 1-32d we are told, that distance has little or nothing to do with heat in this respect.

Again we are told, that if it were not for the projectile force which has been impressed on the Earth, it would be drawn in contact with the Sun by his centripetal power; and yet in accounting for the causes of the Tides, the Moon, which is the Earth's satellite, is supposed to have several times the power on the marine fluid that the Sun has.

And lastly, the Tides are said to follow the motions of the Moon, and as this following is not immediate, but three hours after the Moon's passage, it is assigned, that the active principles of attraction must be allowed that time to operate on the water, yet in the case of the Trade Winds, they take place three hours preceding the Sun, and what can be said for this diversity

If it were true that the Sun guides the Winds by rarefaction, the consequence would be, that wherever the Sun is vertical, the Winds would all rush from every point of the compass, towards that particular spot; thus there would accompany the Sun's path round the circumference of the Earth, a diurnal tornado. It must be granted that the air at eleven o'clock A. M. is more rarefied than that which is at ten: Why does not this ten o'clock air move towards the eleven o'clock, and the eleven towards the twelve, where the air is still in a higher state of temperature, if rarefaction causes these Winds? Since, however, this is not the case, it may be safely said, that rarefaction is not the true cause that govern the Trade Winds. Another objection presents itself against this doctrine: Why does not this rarefying quality of the Sun operate equally to the

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north and south to the same distance from the Sun, as it proves to be affected to the west, which at nine A. M. is forty-five degrees distant? When the Sun is in either of the solstices, we do not find that these Trade Winds reach far beyond the Sun's path, although at that time, the Sun does not go below. the horizon, to the distance of forty-five degrees from the tropical circles, any part of the twenty-four hours of the day, in consequence of which we know by the experience of those who have visited such parts in those seasons, that they have found the heat to be very troublesome, particularly in northern latitudes; whereas on the same parallel to the west of the Sun, he has been absent one half of the day. Also, Why does not the Sun affect the air near the western shores of Africa and America, when he is vertical to them? It is well known to mariners that frequent these parts, that they must reach from fifty to sixty leagues at least from either shore, before they fall in with the Trade Winds.

Previously to entering on my theory of the Winds, may be necessary in order to explain my arguments to state the following quotations:

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From Ferguson's Lectures, p. 173-174.-" The "air is rarefied, or made to swell with heat; and "of this property, Wind is a necessary consequence. "For, when any part of the air is heated by the "Sun, or otherwise, it will swell, and thereby affect "the adjacent air: and so, by various degrees of "heat in different places, there will arise various "Winds.

"When the air is much heated, it will ascend "towards the upper part of the atmosphere, and "the adjacent air will rush in to supply its place; " and therefore, there will be a stream or current of "air from all parts towards the place where the "heat is. And hence we see the reason, why the "air rushes with such force into a glass-house, or "towards any place where a great fire is made;

and also, why smoke is carried up a chimney, [D] and why the air rushes in at the key-hole of the "door, or any small chink, when there is a fire in "the room. So we may take it in general, that the "air will press towards that part of the world " where it is most heated.

"Upon this principle, we can easily account for "the Trade Winds, which blow constantly from "east to west about the equator. For when the "Sun shines perpendicularly on any part of the Earth, it will heat the air very much in that part, "which air will therefore rise upward, and when "the Sun withdraws, the adjacent air will rush in "to fill its place; and consequently, will cause a "stream or current of air from all parts, towards "that which is most heated by the Sun. But as "the Sun, with respect to the Earth, moves from "east to west, the common course of the air will be that way too; continually pressing after the Sun: "and therefore, at the equator, where the Sun shines strongly, there will be a continual Wind from the "east; but, on the north side, it will incline a little "to the north, and on the south side, to the south. "This general course of the Wind about the equator, is changed in several places, and upon "several accounts: as, 1. By exhalations that rise "out of the Earth at certain times, and from certain "places; in earthquakes, and from volcanos. 2.

By the falling of great quantities of rain, causing "thereby a sudden condensation or contraction of "the air. 3. By burning sands, that often retain "the solar heat to a degree incredible to those who "have not felt it, causing a more than ordinary "rarefaction of the air contiguous to them. 4. By high mountains, which alter the direction of the "Winds in striking against them. 5. By the declination of the Sun towards the north or south, heating the air on the north or south side of the 66 equator.

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"To these and such like causes is owing, 1. The irregularity and uncertainty of Winds in climates "distant from the equator, as in most parts of Europe. 2. Those periodical Winds called monsoons, which in the Indian seas, blow half a year "one way, and the other half another. 3. Those "Winds which, on the coast of Guinea, and on the "western coasts of America, blow always from "west to east. 4. The sea breezes, which, in hot "countries, blow generally from sea to land, in the "day time; and the land breezes, which blow in "the night; and in short, all those storms, hurri"canes, whirlwinds, and irregularities, which happen "at different times and places."

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From Dampier's Disc. of Winds, chap. 4.—" Sea "breezes commonly rise in the morning about "nine o'clock, they first approach the shore gently, "as if they were afraid to come near it. It "comes in a fine black curl upon the water, whereas "all the sea between it and the shore (not yet "reached by it) is as smooth and even as glass in comparison. In half an hour's time after it has "reached the shore, it fans pretty briskly, and so "increaseth gradually till twelve o'clock, then it is commonly the strongest, and lasts so till two or "three, a very brisk gale. After three it begins to "die away again, and gradually withdraws its "force till all is spent, and about five o'clock it is "lulled asleep and comes no more till next morning. "And as the sea breezes do blow in the day and "rest in the night, so on the contrary the land "breezes blow in the night, and rest in the day 'alternately, succeeding each other; they spring up between six and twelve at night, and last till "six, eight, or ten, in the morning."

It has been already shewn in the first part of this work, by experiments, that the extreme of heat and that of cold, is the extreme of power in each; if the temperature is lowered, or the cold is lessened by