Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/88

 of a particular person, by reason of its great distance would be invisible, as I have said before.

I am very apprehensive of your discourse; yet methinks I am able to resolve the same with very little trouble; and easily to maintain, that the Moon is rotund and polite, and that it reflects the Suns light unto us in manner of a glass; nor therefore ought the image of the Sun to be seen in the middle of it, "forasmuch as the species of the Sun it self admits not its small figure to be seen at so great a distance, but the light produced by the Sun may help us to conceive that it illuminateth the whole Lunar Body: a like effect we may see in a plate gilded and well pollish'd, which touch't by a luminous body, appeareth to him that beholds it at some distance to be all shining; and onely near at hand one may discover in the middle of it the small image of the luminous body".

Ingenuously confessing my dullness of apprehension, I must tell you, that I understand not any thing of this your discourse, save onely what concerns the gilt plate: and if you permit me to speak freely, I have a great conceit that you also understand not the same, but have learnt by heart those words written by some one out of a desire of contradiction, and to shew himself more intelligent than his adversary; but it must be to those, which to appear also more wise, applaud that which they do not understand, and entertain a greater conceit of persons, the less they are by them understood: and the writer himself may be one of those (of which there are many) who write what they do not understand, and consequently understand not what they write. Therefore, omitting the rest, I reply, as to the gilt plate, that if it be flat and not very big, it may appear at a distance very bright, whilst a great light beameth upon it, but yet it must be when the eye is in a determinate line, namely in that of the reflex rays: and it will appear the more shining, if it were v. g. of silver, by means of its being burnished, and apt through the great density of the metal, to receive a perfect polish. And though its superficies, being very well brightned, were not exactly plain, but should have various inclinations, yet then also would its splendor be seen many ways; namely, from as many places as the various reflections, made by the several superficies, do reach: for therefore are Diamonds ground to many sides, that so their pleasing lustre might be beheld from many places. But if the Plate were very big, though it should be all plain, yet would it not at a distance appear all over shining: and the better to express my self, Let us suppose a very large gilt plate exposed to the Sun, it will shew to an eye far distant, the image of the Sun, to occupy no more but a certain part of the said plate; to wit, that from whence the reflection of the incident