Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/105

 darknesse; for that that matter which admits the passage of the Suns rayes thorow a space of two thousand miles, must needs be so transparent, that it would very weakly resist them in a hundredth, or lesser part of that thicknesse; neverthelesse, the term which separateth the part illuminated from the obscure, is incident, and as distinct, as white is distinct from black; and especially where the Section passeth through the part of the Moon, that is naturally more clear and montanous; but where the old spots do part, which are certain plains, that by means of their spherical inclination, receive the rayes of the Sun obliquely, there the term is not so distinct, by reason of the more dimme illumination. That, lastly, which he saith, how that the secondary light doth not diminish and languish, according as the Moon encreaseth, but conserveth it self continually in the same efficacy; is most false; nay it is hardly seen in the quadrature, when, on the contrary, it should appear more splendid, and be visible after the crepusculum in the dark of night. Let us conclude therefore, that the Earths reflection is very strong upon the Moon; and that, which you ought more to esteem, we may deduce from thence another admirable congruity between the Moon and Earth; namely, that if it be true, the Planets operate upon the Earth by their motion and light, the Earth may probably be no lesse potent in operating reciprocally upon them with the same light, and peradventure, motion also. And though it should not move, yet may it retain the same operation; because, as it hath been proved already, the action of the light is the self same, I mean of the light of the Sun reflected; and motion doth nothing, save only vary the aspects, which fall out in the same manner, whether we make the Earth move, and the Sun stand still, or the contrary.

None of the Philosophers are found to have said, that these inferiour bodies operate on the Cœlestial, nay, Aristotle affirmes the direct contrary.

Aristotle and the rest, who knew not that the Earth and Moon mutually illuminated each other, are to be excused; but they would justly deserve our censure, if whilest they desire that we should grant and believe with them, that the Moon operateth upon the Earth with light, they should deny to us, who have taught them that the Earth illuminates the Moon, the operation the Earth hath on the Moon.

In short, I find in my self a great unwillingnesse to admit this commerce, which you would perswade me to be betwixt the Earth and Moon, placing it, as we say, amongst the number of the Stars; for if there were nothing else, the great separation and distance between it and the Cœlestial bodies, doth in my opinion necessarily conclude a vast disparity between them.