Now, by the certain Return of the Comets, which we find are all governed by the Laws of this System, and supposed to be undisturbed by any of the others, we cannot avoid concluding, if we consider them at all to the Purpose, that the nearest Stars cannot be less distant than twice the Radius of the greatest Orbit belonging to the Sun. Most Mathematicians think this a great deal too near, as it must of course make all the Systems join, as in Contact; and I think we may safely add, to separate their Spheres of Attraction, at least one Half of this Distance more, which will make in the Whole about four hundred and twenty Semi-orbits of the Earth, or 33,600,000,000 Miles. This even the ingenious Mr. _Huygins_ endeavours to prove still much too little, and his Arguments are such as cannot easily be refuted. His Principle is grounded upon the known Laws of Analogy, as considered in the Proportion of light Surfaces, and is as follows. Having reduced the Sun's Disk to the Appearance of the Star Syrius, by the Help of a small Hole at the End of his Telescope, and comparing this Part of his Surface to the whole Disk of the Sun, he infers that the Stars Distance to that of the Sun must be as 27,664 to 1. Hence _Syrius_ from us will be nearly (avoiding Units) 2,213,120,000,000 Miles: But this I take to be as much too large as the former is too little; yet, as Mr. _Bradley_ has, with some Shew of Reason, banished all the Stars out of the Sphere of Parallax, the last is the only Method we can possibly make use of with any kind of Confidence; and Sir _Isaac Newton_ endeavours to recommend it with great Force of Argument, as the only probable Means by which we can give any tolerable Guess at these immense Measurements of Space. To moderate the Matter then if you please, allow me but to make use of a Mean betwixt the two fore-mentioned Numbers; and we may take it for granted, a Distance sufficiently exact, to suit all our Wants in the present Case, namely, to give a very tolerable Idea of the Extent of the visible Creation, which is all I propose in this Place to attempt; but I mean to be much more exact in another.