And Light of those eternal Rays,
The uncreated Mind displays.
[S] Mr. Bradley, Astronomer-Royal, has, in a great measure, proved that the Aberration of the Stars hitherto mistaken for a Parallax, may arise from, and indeed seems to be no other than the progressive Motion of Light, and Change of Place to the Eye, arising from the Earth's annual Motion and Direction.
It remains now I think to shew, and endeavour to prove, that the Stars are not only light Bodies of the Nature of the Sun, but that they are really so many Suns, all performing like Offices of Heat and Gravity, in a regular Order, throughout the visible Creation, in opposition to an Opinion you have formerly hinted at, of their being in another Sense of a secondary Nature.
All Objects within the sensible Sphere of the Sun's Attraction, or Activity, are in some measure magnified by a good Telescope: But the Stars are all placed so far without it, that the best Glasses has no other Effect upon them than making them appear more vivid or lively, but all innate opaque Bodies, reflecting only a borrowed Light from some primary one, contrary to this Property, are all observed to lose their Light, in the same Proportion, as they are magnified, and through all Glasses become more dull than otherwise they appear to the naked Eye: And hence we may infer, without any further Evidence, that the Stars are all light Bodies endowed with native Lustre; and that Bodies, like the known Planets, from the same Reasoning, it is as clear they cannot be, because their Distance, though uncertain as to the Truth of the whole, yet such a Part of it as cannot be denied, would render them all in such a Case invisible.
A Proof of this will plainly present itself, if we consider the Course of the known Comets, who all of them, without Exception, become imperceptible, and intirely disappear; though most of them much bigger than the Earth, or any of the lesser Planets, long before they arrive at their respective Aphelions.
But we are under a kind of Necessity to believe them either Suns or Planets, that is either dark or light Bodies; and since I have shewn the Improbability; nay, I may venture to say, the Impossibility of their being the first, it is natural sure to conclude, that they must be of the last Sort; and I am persuaded, if you but once consider how ridiculous it is to imagine so vast a Number of Bodies, all rolling round a Number of invisible Suns, which must otherwise be the Case, since they are seen on all Sides of ours, and cannot possibly be enlightened by him, or any, how all of them, by any one else, you cannot possibly have any sort of Difficulty in this Determination: But that no Arguments may be wanting to enforce your Belief of what is here concluded, it will not be amiss to put you in Mind of an optical Experiment or two, which cannot fail of convincing you of the vast Probability of what is here asserted of them; and next to a moral Certainty, demonstrate the Truth of what so many of the best Astronomers have advanced, as before namely, that the Stars are all, or most of them, Suns like ours.
Place any concave Lense before your Eye, and you will find all visible Objects will appear through it, as removed to a much greater Distance than they really are at, and reciprocally as much diminished. Now, if you look upon one of these Glasses of a proper Concavity, opposed to the Sun or Moon, you will respectively have the Appearance of a real Star or Planet, the first exhibited by the Body of the Sun, the other by the Moon, and either more or less diminished in Proportion to the Surface of the Sphere the Glass is ground to.
For Example, a double Concave, or Glass of a negative Focus, ground to a Sphere of about three Inches Diameter, will if opposed to the Sun's Disk at a proper Distance from the Eye, help you to a very good Idea how the Sun appears to the Planet Jupiter; and if a proper Regard be had to the Distance of the Planet Saturn, a Lense still more concave may be formed to give a just Idea of the Sun's Appearance to Saturn. Again, one much more concave than the former, proportioned to the Orbit of Mars, will naturally exhibit the solar Body, as seen from that Planet.
To the Planet Venus and Mercury, the Sun appearing much larger than to us at the Earth, to have any tolerable Notion of his varied Phænomena to them, it will be necessary to procure Glasses of a suitable Convexity, ground to reciprocal Concaves, which may easily be done to any Focus, so as to shew how the Sun, naturally appears to the Inhabitants of those two Planets.