no cause of any considerable change. And allowing, what is probable, that not only the celestial bodies, but also the earth, acts upon the regions of the air; either by breathing out cold, dircharging winds, or the like; yet all this variety may happen in those regions of the earth which lie near the surface; and where no one can doubt but there are numerous changes and revolutions.

But of all the phenomena of the earth; earthquakes, and accidents of the like kind, must be allowed to penetrate by far the deepest; as the eruption of water, the eructation of fire and flames, chasms, and falling in of the earth, &c. and yet these do not happen at any great depth; as most of them usually affect but some little space on the surface of the earth, without spreading far: For the wider an earthquake, or the like, should spread upon the earth's surface, the deeper its origin must he conceived, and vice

versa.

It is true, there sometimes happens such earthquakes, as shake very large and spacious coun

* This, though probable, may require to be better confirmed, because the force that was great at first, and exerted on the central parts, might be suspected to diminish near the surface; so as not there to produce any very considerable effect.

tries; though these are not frequent; but extraordinary cases; and may therefore be, pertinently, compared to the comets, which also appear but seldom: For the business here is not to maintain the immutability of the earth; but only to shew there is no great difference betwixt the heavens and the earth in point of constancy and change.

And further: that the internal parts of the earth are not more subject to corruption than the heavens themselves, may be argued from hence; that things usually decay and perish, where they may be recruited and renewed. For as showers and other falling meteors, which renew the face of the earth, can, by no means, penetrate to its internal parts; which, nevertheless, maintain their bulk, and quantities; it should seem to follow, that nothing is there lost; as there is nothing at hand to repair any loss. *

*This conjecture may receive some light from the converse thereof, which is intimated by Sir Isaac Newton in his Principia, upon better grounds, perhaps, than he there expresses; viz. that as the sea is absolutely necessary to the constitution of the earth, in order to afford a sufficient quantity of vapour, which is raised by the sun; and being either condensed into clouds, falls back again in rain, to water and supply the earth, for the production of vegetables; cr

Lastly, the mutability observed in the more external parts of the earth, seems only accidental: For the thin outside crust, which appears to reach but a few miles downwards, and to contain the two wonderful laboratories of plants and minerals, would receive little variety, much less produce such beautiful and elaborate works, without feeling the influences and perpetual animation of the celestial bodies. To imagine that the heat and active powers of the sun, and other celestial bodies, may strike quite through the entire body of the terrestrial globe, must be a strange degree of superstition and enthusiasm ; whilst it plainly appears how small an object is sufficient to check and restrain them.

No sure argument for the immutability of the

else being condensed upon the cold tops of mountains, runs down into springs and rivers; so, comets seem necessary for supplying the seas, and proper moisture in the planets; that what liquors are there consumed in vegetation and putrefaction, and converted into dry earth, may be seasonably recruited and made good, by the exalations and vapours of the comets. For all vegetables wholly receive their growth from liquids; and afterwards turn, by putrefaction, in great measure, to dry earth. Whence the bulk of dry earth is perpetually upon the increase, and liquids, unless otherwise supplied, perpetually upon the decrease, so as to fail at last. Princip. Lib. III. page 473.

* That is owing to causes from without.

heavens, can be drawn from hence; that the ef fects thereof are not visible: for the sight is frustrated as well by distance, excess, or defect of light, as the subtilty or minuteness of the object: So an eye placed in the moon could not discover the changes which happen here upon the the earth's surface; such as inundations, earthquakes, and the like; for these are but as atoms at so greal a distance. Nor is it safe, because the interstellar heaven appears transparent, and the fixed stars, on clear nights, appear the same, both in number and complexion, to pronounce from thence that the entire body of the æther is clear, pure, and unchangeable: For the air receives numberless varieties of heat, cold, odours, and mixtures, of all kinds, in subtile vapours, and effluvia; and yet appears transparent. So likewise the clear face of the heavens is no proof of their purity, homogeneity, and incorruptibility. For if those huge masses of clouds, which sometimes overspread the heavens, and, by reason of their nearness to us, hide the sun and stars from our sight, were to float in the higher parts of the heavens, they would not at all sully or obscure the clearness thereof: As themselves could neither be seen, on account of their distance, nor darken the stars, on account of the smallness of their body, with regard to

*

the body of the stars so near them. Even the body of the moon does not alter the face of the heavens, except on that half which receives the sun's light; so that, were it not for that light, even such a vast body as the moon would be perfectly hid from us.

On the other hand, it plainly appears from those masses of bodies, which by their bulk and size supply their want of nearness; and which, by means of their luminous matter, briskly strike the eye; that there are strange and extraordinary changes in the heavens. Thus the higher comets, seen in the form of stars, without their tails, are not only by the doctrine of the parallax, demonstrated to be above the moon, † but have also been found to preserve their own figures, stations, and constancy, for some time, like the fixed stars; without wandering in the manner of planets. And such comets have more than once appeared in our time; First in Cassiopeia, and again in Ophiucus: ‡ That this constancy of the comets should proceed from their waiting upon some certain star, which was the

* Compare this with Sir Isaac Newton's doctrine of the Tails of Comets. Princip. Lib. III. page 466, 467, 468, &c. † See Newton. Princip. Lib. III. Lem. IV.

See the author last mentioned. Princip. Lib. III page 455, &c. and Wolf. Elem. Astron. page 594.