+--------+---------+----+----+----+ | 50000 | 1476529 | 14 | 25 | | | 60000 | 1771835 | 12 | 30 | | | 70000 | 2067141 | 10 | 35 | | | 80000 | 2362447 | 8 | 40 | | | 90000 | 2657753 | 6 | 45 | | | 100000 | 2953059 | 4 | 50 | | +--------+---------+----+----+----+ | By comparing this Table with | | the Table on page 113, it is | | easy to find how many Lunations | | are contained in any given | | number of Sidereal, Julian, and | | Solar years, from 1 to 8000. | +---------------------------------+ CHAP. XX. _Of the fixed Stars._ [Sidenote: Why the fixed Stars appear bigger when viewed by the bare eye than when seen through a telescope.] 391. The Stars are said to be fixed, because they have been generally observed to keep at the same distance from each other: their apparent diurnal revolutions being caused solely by the Earth’s turning on its Axis. They appear of a sensible magnitude to the bare eye, because the retina is affected not only by the rays of light which are emitted directly from them, but by many thousands more, which falling upon our eye-lids, and upon the aerial particles about us, are reflected into our eyes so strongly as to excite vibrations not only in those points of the retina where the real images of the Stars are formed, but also in other points at some distance round about. This makes us imagine the Stars to be much bigger than they would appear, if we saw them only by the few rays which come directly from them, so as to enter our eyes without being intermixed with others. Any one may be sensible of this, by looking at a Star of the first Magnitude through a long narrow tube; which, though it takes in as much of the sky as would hold a thousand such Stars, yet scarce renders that one visible. [Sidenote: A proof that they shine by their own light.] The more a telescope magnifies, the less is the aperture through which the Star is seen; and consequently the fewer rays it admits into the eye. Now since the Stars appear less in a telescope which magnifies 200 times than they do to the bare eye, insomuch that they seem to be only indivisible points, it proves at once both that the Stars are at immense distances from us, and that they shine by their own proper light. If they shone by borrowed light they would be as invisible without telescopes as the Satellites of Jupiter are: for these Satellites appear bigger when viewed with a good telescope than the largest fixed Stars do. [Sidenote: Their number much less than is generally imagined.]