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from aloft and therefore, in great storms, they first lower their yards, and down with the topsails; and next, if there be occasion, down with all the rest; even cutting away the masts themselves, and throwing their guns, lading, &c. over board; to lighten the ship, and keep her floating, at the mercy of the waves.

With a brisk and favourable gale, even a ship of burden may sail a hundred and twenty Italian miles in four and twenty hours. There are certain packet-boats, wholly built for sailing, that will make much more way. But when the wind is directly in their teeth; as a last, though feeble shift to advance, they traverse, or cut away cross and cross, out of their course; shifting their sails as the wind requires; then bend up towards their course again: and thus by repeating their angular trips, they get right forwards; though perhaps but at the rate of fifteen miles in twenty-four hours.

LARGER OBSERVATIONS.

THIS motion of the winds, in the sails of ships, has three principal origins, and fountains of its impulse, from whence it is derived; and from whence also, rules may be formed for increasing and strengthening it.

The first fountain is, from the quantity of the wind received; for it is plain, that much wind, here contributes more than a little; and there

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fore a sufficient quantity of wind must be carefully procured. The means to procure it is, in the way of thrift aad good husbandry, to prevent being robbed of it; and therefore, as much as possible, let no wind be lost, misemployed, or taken from the ship.

The wind blows either above the ship's sides, or below them, towards the surface of the sea; and as, in the way of good husbandry, it is usual to be very careful of small matters, (for every body takes care of large ones); so a particular regard must be had to these lower winds; though they doubtless are of less efficacy than the higher.

As for the winds which play chiefly about the ship's sides, and under the sails; it is the true of fice of the main-sail of the bow-sprit to prevent their being lost this mast standing low, and aslope, so that its main-sail may receive them; and therefore become serviceable, without taking from the winds intended to fill the other sails. And, with regard to this point, we do not see what human industry can do more; unless it were to spread the like kind of low sails, in the manner of wings, from the middle of the ship; two on both sides; when the wind blows fore-right.

In order to prevent the fore-sails from being robbed by the back-sails, in fore-right sailing; there seems to be no other method left, but to

range the sails in the form of a pair of steps, mounting upwards from stern to stem, so that the sails of the mizzen-mast may hang the lowest, those of the main-mast in the middle, and those of the fore-mast highest; whence one sail will not hinder, but rather assist, and serve another; by giving and transmitting the wind thereto. But this only holds good in sailing ber fore the wind; for in a side wind, all the sails co-operate. And so much for the first fountain of impulse.

The second fountain of impulse arises from the manner wherein the wind strikes the sail; for if, through the contraction of the wind, the stroke be sharp and sudden, it will give the greater motion; but if diffused and languid the less.

And with regard thereto, it is of very great moment, that the sails should receive but a moderate swell and extension: for if they be too tort, they will rebound the wind like a wall; and if too slack, the impulse will prove weak.

And here human industry has succeeded in some particulars, though rather by chance than by judgment; for, in a side wind, they contract that part of the sail, as much as possible, which is opposite to the wind; and by this means throw the wind into the other part where they would have it blow. And this, indeed, they do

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by design; though, perhaps, without considering, that besides this, the wind is at the same time necessarily contracted; and so has a sharper percussion.

What farther improvement may here be made, we do not well perceive; unless the figure of the sails were altered; and some of them made not to swell spherical, but spur-fashion; with the yard in the middle of the bend: so that the wind, being contracted towards a point, might not only have a smarter percussion; but the sail also the better cut the resisting air. And we know not what might be the effect of having a sail within a sail: that is, to fix a kind of purse in the middle of a large sail; and keep it astrut with splices of wood; so as to collect the wind in the middle of the large sail, and bring it to a kind of point.

The third fountain of impulse, proceeds from the place where the percussion is made; and is of two kinds: for the impulse is easier and stronger on the fore-part, than on the hind part of the ship; and on the upper-part of the masts and sails, than on the lower.

Nor do men seem to have been ignorant hereof; as laying the greatest stress upon the sails of the fore-mast in sailing before the wind; and spreading their main-top-sails in calms. And we can think of no farther improvement, at present,

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in this respect; unless as to the first case, it be to have two or three fore-masts; the middle one erect, and the others inclined, with their sails hanging right-down; and in the second, to enlarge the fore-mast sails, at the top, or to make them less tapering than usual: but in both cases so as to prevent all danger from sinking the ship

too much.

III.

Of the motion of the wind in other machines of human invention.

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And

THE motion of a wind-mill has no difficulty in it; and yet it is, usually, neither well demonstrated nor explained. The sails are set directly facing the wind that blows; but one side of each sail lies more to the wind, whilst the other gradually slopes away from it. But the revolving motion always begins from the lower side; which is farther removed from the wind. now the wind, blowing against the machine, is compressed by the four sails; and obliged to take its course through the open spaces between them whence the wind in this compressed state, of necessity brushes smartly against the edges of the sails, and turns them round; as a top, or the like, is turned, or set up, by a flirt of the finger.

If the sails were stretched out equally, it is a question which way they would incline; as in

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