precipitate, for if it should precipitate, its nature must be changed. What else should cause that, which before ascended of itself, and diffused itself in water, now to precipitate, and separate itself from the water. And perhaps, no other particles, that are to be found in any considerable plenty in the earth, except Salt, are of such a nature, that they will, of themselves, diffuse themselves in water, and so continue, without either precipitating again, or gathering at the top, or some way separating. Other particles may do so, because they are united to particles of Salt, as the particles of Alum, and other things, that very much consist of salt particles. But yet, it is probable, that, in length of time, these foreign particles, being disengaged from the Salt, may precipitate, or ascend, and leave only pure Salt. 5. It must be considered, that Salt will, of itself, dissolve, and mix itself with water to such a degree, that the water is, as it were, satisfied; and then, how much Salt soever is thrown in, it precipitates, and refuses to mix with the water. 6. It follows, from these considerations, that, except the water of the sea be so full of Salt, that it can hold no more, all the Salt, that ever happens to mix with the water of the sea, will be there retained. 7. It follows, that, if the water be not saturated with Salt, or has not as many salt particles as it can retain, that the water of the sea could never yet come at Salt enough, to saturate it; and that, though all the Salt that the sea washes, and all the salt particles that ever were in any way carried into the sea, are now combined with the water of the sea, yet, there is not enough to saturate it, inasmuch as it retains all that it gets, until it be satisfied. 8. It may be considered, that, besides the Salt, which is diffused in the sea, from those beds which the sea washes, it holds all the saline particles, that are carried into it by all the rivers; and, though they should be but few in a little time, yet, because the sea discharges itself of them no more, but the water, when it returns, by exhalation or otherwise, leaves them behind, coming forth perfectly fresh, in whole ages, the rivers would carry in enough to make the sea salt. For there are a multitude of salt particles in the upper mould of the earth, as appears, in that plants have so much Salt in their constitution. And the rivers must needs bring a multitude of these: especially, in times that they overflow their banks, great quantities must be carried into the rivers by rains, and the melting of snows: so that, it is impossible, but that the Sea, in process of time, should be salt. 73. EXHALATIONS. Relating to No. 57. I do not know whether any other liquid is exhaled after this manner. Oil, we know, may be exhaled, though very difficultly and slowly; and whether it be by bubbles I cannot tell. I believe that nothing but what is liquid is exhaled, or caused by heat, or the sunbeams, to ascend in the Atmosphere after this manner, by being rarified so as to be buoyed up by the mere weight of the Atmosphere; because the properties of a liquid body seem necessary to such a rarefaction. For, in order to the being capable of such a rarefaction by the sunbeams, it is necessary that the body should easily receive the impression of rays, to diffuse it abroad or to expand its parts: and yet the parts must so cling one to another as totally to exclude the circumjacent air from filling the places that were left empty by that expansion. For, how much soever the parts are expanded, yet if air comes in between the scattered parts, there will not be less matter or weight within its bounds, than in a like quantity of the rest of the air, and so the rarified body would not ascend in the air. And yet I am very far from thinking, that there are none but liquid exhalations, or that no bodies are caused to ascend into the air by the sunbeams, but liquids, or that liquids are the vehicles to all exhalations. I be lieve that particles of every kind are caused, by the sunbeams, to diffuse themselves all over the Atmosphere, after the same manner as odours are diffused, and those constituent parts of the Atmosphere, which we spake of when treating of the Atmosphere. (See No. 56.) And it is easy to conceive, that many of those particles, when a sufficient number of them happen to get together, should be capable of creating heat after the same manner as the particles of the Sun, and to any degree of intenseness, and with any degree of suddenness. 74. CLOUDS. I think I have not seen it explained, with respect to the clouds, why they are terminated by such even and distinct bounds; especially in those clouds that we call Thunder-clouds. The clouds are nothing else but vapours, that are drawn up from all parts of the sea and earth, and, one would think, should be scattered every where in the air indiscriminately, so as to thicken the whole upper region of the air. Or, if the air were thickened by them in one place more than in another, because a greater number of vapours are drawn up from some parts of the earth than others; yet, as they fly loose in the air, one would think they should be terminated very gradually, growing thinner and thinner by little and little, till at last it should be so thin that it could not be discovered. But, instead of that, we see the clouds terminated by very distinct surfaces and bounds. They are extended thus far, and then cease at once, and all beyond is clear air. Sometimes indeed, the air is thus universally thickened, as when Halos or Parhelions appear; but afterwards these vapours gather into distinct heaps and thick clouds. I do not know, that this can be explained any other way, than by the mutual attraction of the parts of the vapour, that they thus run together, and make such distinct heaps. The only difficulty is, How, according to the laws and just proportion of attraction, the attraction of such small parcels of matter to each other, should be great enough to explain exceedingly this. To this I answer, That the attraction need to be but exceedingly small, to make these parcels to draw nearer and nearer together, so fast as is needful to suppose they do, when they hang so free in the air, when the air is so thin, and they so high, and their mutual attraction is so little hindered by the attraction of other bodies. If we suppose that two bubbles, that are at the distance of an hundredth part of an inch, moye so fast towards each other, as to get together in three, four, five or six hours, it will be enough. When there is a very still and calm air, and the vapours are ascended very high, whence they are more at liberty, we see them collected into parcels nearly of an equal bigness, and at an equal distance; so that the heavens appear checquered with them. This is the very natural effect of this mutual attraction. After the same manner, when we breathe upon glass; though at first the vapour is every where equally spread over the glass; yet the particles, by their mutual attraction, presently run into such like parcels. 75. RAIN. The reason why the winds, that blow from the coasts, bring rain, is not merely because they are more impregnated with watery vapours; for such winds will thicken the air with clouds, in regions very remote from the sea, as soon as they begin to blow, before they can possibly bring any vapours so far. And besides, if that were the only reason, it would always rain in the midst of the ocean. But the reason seems to be this: When the wind blows from the sea, towards the mediterranean regions, the stream of the air is up hill, so as it is when the wind passes over a mountain. The vapours are suddenly lifted so high by the wind, that the air is too thin to support them. You may see the reason of it plainly thus : When the air is in equilibro on the continent, A B, the strata a trary, occurs when the wind blows from A to B,the vapours are not all hoisted, but carried into a thicker region, that is better able to support them. and then it is fair weather. 76. WINTER. The reason, why there are more frequent and violent winds in winter than in summer, is, because the air by reason of cold being more dense, hangs together, and does not give way but in a body. Winters are very useful upon this account, that the frost loosens the soil every year, which otherwise would bake down very hard. 77. ICE. COLD. Those Nitrous particles, that are said to be thrust into the water, in the process of freezing, do not keep themselves immoveable after the manner of wedges, by filling up the spaces between, so that they shall not have room to play and move freely among themselves; for this hypothesis still leaves the matter inexplicable. For 1. It is inexplicable how these wedges should thrust themselves in so fast, into a heap of particles so exceedingly moveable, that they cannot be stirred at all: how these wedges should be of so happy a shape, and should so happily, each of them, find a vacuity among the vacuities of the water, exactly accommo dated to their shape, as to completely fill them up, so that of all these little rolling slippery particles none can stir at all, insomuch that that, which was before a liquid body, shall not only be made something more solid like clay, but should be so hard, as not to give way without breaking. Let us suppose, for the easiness of conceiving, that the particles of water were as big as peas. Let the frigid particles be as big in proportion, but otherwise having all the same qualities. Let a multitude of freezing particles be hovering in the air, over this heap of globules. It is very probable that many of them would get in among the globules, so that perhaps they would not slip, and roll one over another, so easily for it. But it is inconceivable how these Nitrous particles, being hard, should so be accommodated to the angled vacuities, that all the vacuities should be so filled, that the heap of globules should be so hard as to bear a great weight, a hard shock, without any impression being made upon it. But it would be yet more strange if it was evident, that there was more vacuity, now, in the heap of globules, than before, and yet none of the globules should have room to stir; which yet is certainly the case in water, as all know, ice being lighter than water. But this matter of freezing may be easily solved, from the certain princi ples foregoing, of the strong attraction of particles, one to another. Wherefore, to solve the matter, we shall first lay down the following axioms. Ax. 1. Since particles of matter tend to each other, as we have shows. it is evident, that every part of the surface of one particle, tends to touch the surface of another near it, and would touch it, if it were not hindered by protuberances, or otherwise. Ax. 2. Therefore, if a particle that is near to another particle, be flexible, so that it can accommodate its figure and surface to the surface of the particle attracting it; it will, by so accommodating itself, and being thereby brought abundantly nearer, and approaching it in innumerable points, if it be denser, according to the foregoing principles, cleave ex ceeding fast to it, and will not be easily separated from it. Ax. 3. If one of these flexible particles lies between two or more particles, it will, for the same reason, accommodate itself to all their surfaces; and, filling up the vacuity, if it be not too big, will cleave fast to them all, and they all will cleave fast to that. However easily separable they were before, yet now, they will all be held together by this. And if the vacuity be too big, what one particle can't do, two or more can. Ax. 4. If many of these particles were dispersed in the vacuities of a mass of particles, otherwise moveable, they would hold the whole immoveable, one against another. Ax. 5. And if these particles are not flexible, with such a flexibleness as that of leather, and other bodies that are elastic, and are easily capable of stretching, and compression, as well as impression; but with such a flexibleness as that of clay-a dead flexibility, without being capable of rarefaction, compression, or elasticity; the mass of particlest hat are congealed by it, will be hard, and not elastic. Ax. 6. These particles will be capable of entering the smallest pores; for the same quality that capacitates them to accommodate themselves to the surfaces of bodies, makes them capable of being accommodated to pores of any figure or dimensions. Ax. 7. If many of these particles, being of such a flexible nature, are hovering over an heap of very smooth particles, they will be drawn into their vacuities, by the attraction of those particles, after the same manner as, and for the same reason as, water of itself ascends, and is drawn into very small glass tubes. Ax. 8. However flexible these bodies may be, by their own attraction to their own centers, to one another, or to other particles; yet, they may be so dense, and their attraction so great, that a considerable mass of particles, congealed by them, shall be very hard, because the figure cannot be changed, or an impression made, without stirring the whole mass that is contiguous, and so contradicting the strong attraction of a multitude of these particles. And after this manner, I suppose Ice is made; and the only thing that remains to be explained, is-How the freezing, which fills up so many of its pores, should yet make it lighter, or more rare? Which will not be difficult, from the same principles. For according to these principles, it is not at all probable, that the mass of water should be all congealed at once, in one instant, so that every pore will be filled up with them at once; but that, as these particles gradually work into the water, they will be laid hold of, and locked together by parcels, as thecongealing particles get in, till at length, the whole mass is made fast. The mass is stiffened by parcels; which parcels, being made hard and stubborn, will not accommodate themselves to the vacuities that shall be made by the invincible drawing of parti cles out of their seats, by these frigid atoms: whereby, a multitude of vacuities will unavoidably be made. Supposing a parcel of particles, consisting of nineteen, Fig. 1. Fig. 2. should be catched, and fastened as they lie in this form, Fig. 1. It is evi मैं dent, that, by the force of the attraction of the particles, that are between in their pores, these frigid particles being supposed to be flexible and pliable, they will be drawn into such a figure as this, Fig. 2; and this may be done, with invincible force. And by this means, vacuities will be left in the places from whence these particles were drawn, except other particles of water come in their room. But perhaps the particles in the neighbourhood, are stiffening together at the same time; and, instead of coming to fill up the vacuities, made by the congealing of this parcel, they are drawn farther off themselves, and make the vacuity greater. Besides, the slides of the parcel, as. it conforms itself to the figure, (Fig. 2.) will unavoidably thrust out the neighbouring particles, from their places, which, perhaps, are congealed together into stiff parcels. Wherefore, this thrusting must necessarily cause vacuities in another direction, by displacing of these new inflexible parcels of water, which cause the like displacing through the whole mass, as far as particles are contiguous. A Let us still represent the matter in a larger figure, for clearer illustration. Let us suppose the vessel A B C D, (Fig. 3.) full of particles of water, into which the particles of cold getting, glue them together, by parcels, of all manner of irregular figures, and magnitudes: but let us suppose for the present, that there are seven in a parcel, and that the parcels be those which we have marked out by the crooked lines, connecting them. It is all one, as to the room they take up, let them be taken in any other figure whatever. It is evident that they will be drawn into this form, Fig. 3. B (Fig 4.) and that they cannot lie in such a form, without far greater vacuities than before, and that, when they are brought in this form, the surface of the water must be considerably lifted above the brim of the vessel, A B C D, and the water will take up much more room than before, let |