Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/101

 Quadrature, the same appears very weak, because it continually loseth more and more of the view of the luminous part of the Earth: and yet it should succeed quite contrary, if that light were its own, or communicated to it from the Stars; for then we should see it in the depth of night, and in so very dark an ambient.

Stay a little; for I just now remember, that I have read in a little modern tract, full of many novelties; "That this secondary light is not derived from the Stars, nor innate in the Moon, and least of all communicated by the Earth, but that it is received from the same illumination of the Sun, which, the substance of the Lunar Globe being somewhat transparent, penetrateth thorow all its body; but more livelily illuminateth the superficies of the Hemisphere exposed to the rays of the Sun: and its profundity imbuing, and (as I may say) swallowing that light, after the manner of a cloud or chrystal, transmits it, and renders it visibly lucid. And this (if I remember aright) he proveth by Authority, Experience and Reason; citing Cleomedes, Vitellion, Macrobius, and a certain other modern Author: and adding, That it is seen by experience to shine most in the days nearest the Conjunction, that is, when it is horned, and is chiefly bright about its limb. And he farther writes, That in the Solar Ecclipses, when it is under the Discus of the Sun, it may be seen translucid, and more especially towards its utmost Circle. And in the next place, for Arguments, as I think, he saith, That it not being able to derive that light either from the Earth, or from the Stars, or from it self, it necessarily follows, that it cometh from the Sun. Besides that, if you do but grant this supposition, one may easily give convenient reasons for all the particulars that occur. For the reason why that secundary light shews more lively towards the outmost limb, is, the shortness of the space that the Suns rays hath to penetrate, in regard that of the lines which pass through a circle, the greatest is that which passeth through the centre, and of the rest, those which are farthest from it, are always less than those that are nearer. From the same principle, he saith, may be shewn why the said light doth not much diminish. And lastly, by this way the cause is assigned whence it comes, that that same more shining circle about the utmost edge of the Moon, is seen at the time of the Solar Ecclipse, in that part which lyeth just under the Discus of the Sun, but not in that which is beside the Discus: which happeneth because the rays of the Sun pass directly to our eye, through the parts of the Moon underneath: but as for the parts which are besides it, they fall besides the eye."

If this Philosopher had been the first Author of this opinion, I would not wonder that he should be so affectionate to it,