grees of density and firmness.-Or the particles of a body may be firm enough to reflect all sorts of rays, and yet have so little attraction to hold them that the body will be white. Or a body may be compounded of particles aving so little resistance as to reflect no rays, or of so great density as to hold all, or so full of pores as to drink in all. Then the body is black. Or the particles of bodies may have pores and hollows, that may be big enough to let in the least rays, but not the rest; so that the pores of particles may have much to do in the causing of colours.

The Blue of Mountains, at a distance, is not made by any rays reflected from the mountains, but from the air and vapours that are between us and them. The mountain occasions the blueness, by intercepting all rays, that would come from beyond to disturb that colour by their mixture.

It may therefore seem a difficulty, why the Atmosphere all round by the horizon, does not appear very blue; seeing it is evident that the Atmosphere reflects chiefly the blue rays, as appears in the higher parts of the Atmosphere by the blueness of the sky, and near the Earth by the blueness of mountains, and the redness or yellowness of the rising and setting Sun. It should therefore seem that the Atmosphere should appear most blue, where no rays are intercepted by mountains; because the Atmosphere beyond the mountain reflects the rays as well as on this side. Therefore it seems at first that there would be more blue rays come to eyes, where none were intercepted by mountains, and consequently that the most lively blue would be there. And so it would be, if blue rays came to our eyes in the same proportion that they are reflected. But most of those blue rays, that are reflected by those parts of the Atmosphere, that are at a very great distance, are intercepted by the intermediate air, before they come to our eyes; (for the air by supposition intercepts them easiest;) and only those few yellow rays and less reflexible rays, that are reflected by the air, come to our eyes; whence it comes to pass that the Atmosphere near the horizon, does not appear blue, but of a whitish yellow; and sometimes, when it is filled with more dense exhalations, that can reflect less reflexible rays, still, it appears a little reddish.

82. HALO. The reason why there commonly is a Circle, about the Sun or Moon, a little before falling weather, and not at other times, is, be ⚫cause the cavities of the bubbles, when preparing for rain, are lessened, the internal air losing its agitation and heat, and thereby, the skin is necessarily made thicker; from whence it necessarily follows, that a greater proportion of rays will be refracted. When the skin is very thin, there are but very few rays, but what go twice through the skin; but we have shown that only those, that do not go through it at all, are the rays that constitute the circle.

83. LENS ABOUT THE SUN. That vast Lenticular Haze, or Mist, which appears about the body of the Sun, seems to me probable to arise thus. The Effluvia, that are carried off from the opaque bodies of the Solar System, and especially the Comets, by their being carried beyond the attractions of the globes they proceed from, come at length under the government of the Sun's attraction; and so these particles, by virtue of the force impressed upon them, while they adhered to the globes they came from, conjunctly with that that carried them off, proceed to revolve about the Sun. And their motion being gradually lessened, by the resistance of the Ether, their orbits are gradually contracted, and they gather up about the Sun, though their motion is retarded so gradually, that it is a long time before they come quite down to the Sun's body. And the reason, why the planes of most of their orbits are in, or near, the plane

of the Zodiac, is this: for although the planes of the orbits of the Comets, cut the plane of the Zodiac, at all angles, indifferently, so that we suppose, that the planes of the orbits of these Effluvia, are at first inclined to the plane of the Zodiac, at all angles, indifferently; yet, they become less and less inclined to it, by means of the motion of the Ether, which gradually destroys that inclination. For the Planets, by their continual revolutions, drive and draw the etherial matter round, with a motion parallel to theirs. For one Planet, by means of its attractions, and by means of the repelling nature of the particles of Ether, whereby like the air, they repel, and keep at a distance from, one another; I say, by these means, one Planet moves a vast mass of the Etherial matter, and the Diurnal Revolution of the Sun, also conspiring with the Planets, makes the whole go round in a vortex, parallel to the Zodiac. And it is easy to conceive, how this should gradually bring the revolutions of the dispersed particles we are speaking of, nearer and nearer to the plane of theC Zodiac. Let A B be the plane of the Ecliptic. Let CD be the plane that one of these particles first begins to revolve in, about S the Sun. It is plain, that the Etherial matter, turning round every where parallel to A B, when the particle is in the part of its orbit towards D, will hinder its going as far off from A B, that is, from the plane of the Zodiac, as it did before, and will a little impel it towards B; and so, when it comes to that part of its orbit about C, it will impel it a little nearer to A; and so will continually make its revolution to be nearer the Zodiac.

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These things I suppose are certain, about this Misty Lens: Ist. That it is not any reflexion or refraction of the Atmosphere; because, when it appears, before the Sun rises, or after it sets, it does not always appear perpendicular to the horizon, but always according to the Zodiac; therefore, 2d. That it must be a reflection of the Sun's light, from some matter that really en-. compasses the body of the Sun.

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84. MOON. There is a very evident token of design and providence, in the exact adjusting of the diurnal and periodical revolutions of the Moon. For, although the figure of the Moon is somewhat oval, so that that diameter of the Moon, which, if prolonged, passes through the Earth's centre, is a little longer than the other diameter, that is perpendicular to it, by about 187 feet; so that the attraction of the Earth, by this means, would preserve this exact equality, notwithstanding very small disturbance; yet except the forces, that first gave the Moon these revolutions, had been very exactly equable, this small inequality of the diameters would in no wise have kept the same face of the Moon turned towards us; nor would it ever have reduced the revolutions nearer to an equality, than they were at first. For, except the disproportion had been infinitely small, it would have been sufficient to turn the Moon, so that every side should be turned towards us: and the diurnal revolution would have been accelerated, every time the longer axis of the Spheroid began to be turned towards the Earth, so as to point to it, and retarded when it turned from it. Though this exact equality of these two motions, be of no great use to us, as we know of; yet, probably, it is of great use to them; for if, in its revolutions, all sides of the Moon were turned to the Earth, the seas, if there be any, would be raised 97 feet high; which Tide would probably be very destructive to the surface of that planet.

The Moon's Atmosphere is so very thin, that, in their long days, they might not be too hot: so thin a fluid not supplying matter adapted to those agitations and vehement motions, which is heat.

85. YEAR. The wisdom of God appears, in making the Year of such a length; because, if the year were much shorter, there would be very little of a regular distinction of seasons, by cold and heat. Before the air and earth would have lost the heat of the summer Sun, the Sun would be in the Tropic of Capricorn; and before we should have got over the cold of the Sun's absence in winter, the Sun would be again over our heads, and the seasons would be confounded.

86. COMETS. The use of Comets seems to be, by their effluvia, which go off in their tails continually, but especially in their perihelion, to feed the Sun with matter, suitable to be converted into rays of light, to repair the waste of such particles, by the vast diffusion of light which it daily emits. They are sent out of the atmosphere of the Comet, not as rising by the weight of their circumambient Ether; for it has been demonstrated to be so small, and so near to nothing, that it is not supposable, that it can be by any such means; but by the force or attraction of the emitted rays of the Sun, which, passing through the atmosphere of the comets, by their attraction, draw after them, continually, those particles, of which the tail is made up. The rays, that pass by very near them, act upon them by their attraction, and set them into a motion from the Sun, and parallel to the motion of the emitted rays of the Sun. There is no matter, by this means, sent out of the atmosphere into the tail, but that which is most suitable to be the aliment of the Sun, and to be converted into rays of light; for the rays of light attract that matter, that is of their own nature, and suitable to be turned into particles of light, or fire, immensely more strongly than others, as appears, by the action of particles of light, or fire, upon natural bodies, in setting them on fire. Their action is, at first, on those particles in the natural body, that are of the same kind, or fit to become particles of fire, and, by this attraction of extrinsic rays, those within are set in motion, whereby the body is set on fire. And thus, by the powerful action of those particles, one on another, there arises that most rapid and vehement motion of them in fire, and causes them to leap forth, with such immense celerity, as to come from the Sun hither in a few minutes. This strong action of these particles, one on another, probably arises from their being immensely denser than other particles.

87. FIXED STARS. The motion of the Fixed Stars backwards in the Ecliptick, if it be not real, but be caused by any motion in the Earth, must necessarily be caused by a motion of the poles of the Earth round the poles of the Ecliptick, in a circle equal to the Polar Circles. For it is most certain, if this motion is in all the Fixed Stars, in circles parallel to the Ecliptick, that then the Polar Star itself moves round the Pole of the Ecliptick in a circle equal to the Polar. But seeing the Pole Star itself stirs not, the apparent motion of it, from the Pole of the Earth, must be by the motion of the Pole. For either the Pole moves, or the Star moves, it is certain. Besides, it is certain, if the plane of the Equator moves, the Poles move. But if the points of intersection that this plane makes with the plane of the Ecliptick, move, the plane itself moves, if the Ecliptick itself move not. And the motion must be such as to cause the Poles to move round the Pole of the Ecliptick. In such a manner and sense, in the Ecliptick, the Fixed Stars move a degree in 70 years. It follows that the Pole of the Earth will move quite round this circle in 25,200 years.

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From hence it is certain, if the Fixed Stars move not, that the Earth has two rotations upon two different Axes:-one à Diurnal, upon the Axis that runs from the North to the South Pole; another, that is performed in 25,200 years, upon the Axis that runs from one Pole of the Ecliptick to the other, the last being about a mile in a year, under the Ecliptick, being perhaps about as fast as a snail would crawl, and might possibly be caused by some Comet passing by the Earth in the plane of the Ecliptick. Now there would be exactly such a rotation upon the Axis of the Ecliptick, by a Comet's coming near the Earth, if in the plane of the Ecliptick, in its descent towards the Sun; for the Earth would be stretched somewhat into an Oblong Spheroid, in such a case; and as the comet went along, it is evident, that that end of the Spheroid that was next to it, would, in some measure, follow it or be drawn after it, which would beget just such a motion.

88. ATOMS. It is certain that, when God first created Matter, or the various Chaoses of Atoms, besides creating the Atoms and giving the whole Chaos its motion, he desigued the figure and shape of every Atom, and likewise their places; which doubtless was done with infinite wisdom, and with an eye to what should follow from the particular bulk, figure and place of every Atom; and this be so ordered that, without doing any thing more, the Chaoses of themselves, according to the established Laws of Matter, were brought into these various and excellent forms, adapted to every of God's ends, excepting the more excellent works of plants and animals, which it was proper and fit God should have an immediate band in. So the Atoms of one Chaos were created in such places, of such magnitudes and figures, that the Laws of Nature brought them into this form, fit, in every regard, for them who were to be the inhabitants.

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AXIOMS. 1. If a thing is to come one of two or more ways, if it happen in one of those ways, and not in another, it will be because there is some reason why it should happen this way, and not another, And in things that have happened, there is some reason, why they have happened this way more than another. For instance, I say it is evident, that if the body C be at rest, but is to move either towards A, or B, or D, or E, if it move towards E, it will be because there is some reason why it should move towards E, more than why it should move towards A, B, or D.

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2. Which necessarily follows from the former; when there is an equal reason, why the thing should be, or happen each of the supposed ways, and it cannot be all, it will be neither. If it can be proved that there is equal reason why the body C should move towards either A, B, D, or E, it will move towards neither of them.

3. The same force will equally separate all bodies, or parts of bodies, conjoined with equal strictness, ceteris paribus,-This to prove that it holds in all Atoms.

4. Nothing produces Any thing where it is not. There is no need of inserting the word immediately here; for in the sense of this Axiom, that only, which immediately does a thing, properly does it. For instance, when one body is thrown against another, and causes that other body to move; in the sense of this Axiom, it was the body that was thrown, that

moved the other, and not the man that' threw it. The Axiom is evident, because it is a contradiction to suppose that the body acts where it is not, or to say that it exerts itself, where itself is not. It is evident that, if a body be not in such a space, that it is all one with respect to that space, as if it had no existence at all.

5. Wherefore, if a body is placed alone in a space, as for instance, the body C, in the midst of the space A B E, there being no other corporeal being in that space; if this body be at rest, and afterwards it begins to move, it is manifest that it is not moved by any corporeal being, but by a being A not corporeal. Or if the body C be held at rest, so that it cannot be moved, it is evident it is held there by an incorporeal being.

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6. For the same reason, if the two bodies e, and o, touching each other, be touched by no other body, if the body e, be held to the body o, so that it cannot be moved away from it, it is evident that it is held there by an incorporeal being; for the body o, cannot possibly act upon the body e, so as to hinder it from moving away; for by Axiom 4, the body o does not act where it is not; but the body o, is, no further than its surface is. And the case will be the same, let the bodies touch in one point, or in more, or by lines or surfaces; as the bodies a, and v. If v cannot be moved towards y, it must be an incorporeal being that keeps it immoveable; for a is present no farther than the plane fm, and therefore cannot possibly act on v, which is beyond it, to hinder its being moved towards y.

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POSTULATUM. The attraction of small bodies, is so much greater than the attraction of great bodies, according to the quantity of matter in them, at the same distance from the surface of each, as the squares of the distances of the parts of the small body are less. For the parts of small bodies attract bodies nigh to them immensely more than corresponding parts of great bodies, because the parts of a small body may lie so much nearer to the body attracted. Therefore, small bodies attract bodies near their surface, with immensely greater strength, according to the quantity of matter that is in them, than great bodies, supposing they be equally dense. But the minute particles of bodies have commonly vastly more matter in proportion to their dimensions, than great bodies; and therefore will attract abundantly more, for that reason.

RAINBOW. The separation of heterogeneous rays, in the Rainbow, is not at the reflexion of the concave surface, but at the two refractions going in, and coming out. There is not a distinct Reflexibility, but only Refrangibility.