When I first compared the nature of our earth and water with those appearances in the Moone; I concluded contrary to the proposition, that the brighter parts represented the water, and the spots the land; of this opinion likewise was Keplar at the first.1 But my second thoughts, and the reading of others, have now convinced me (as after he was) of the truth of that proposition which I have now set downe. Before I come to the confirmation of it, I shall mention those scruples which at first made mee doubt the truth of this opinion.
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It may be objected, ‘tis probable, if there bee any such sea and land as ours, that it beares some proportion and similitude with ours: but now this proposition takes away all likenesse betwixt them. For whereas the superficies of our earth is but the third part of the whole surface in the globe,2 two parts being overspread with the water (as Scaliger observes) yet here, according to this opinion, the Sea should be lesse than the land, since there is not so much of the bespotted, as there is of the enlightened parts, wherefore ‘tis probable, that there is no such thing at all, or else that the brighter parts are the Sea.
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The water, by reason of the smoothnesse of its superficies, seemes better able to reflect the Sun-beames than the earth, which in most places is so full of ruggednesse of grasse and trees, and such like impediments of reflexion; and besides, common experience shewes, that the water shines with a greater & more glorious brightnesse than the earth; therfore it should seeme that the spots are the earth, and the brighter parts the water. But to the first it may be answered.
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There is no great probability in this consequence, that because ‘tis so with us, therefore it must be so with the parts of the Moone, for since there is such a difference betwixt them in divers other respects, they may not perhaps agree in this.
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That assertion of Scaliger is not by all granted for a truth.3 Fromondus with others thinke that the superficies of the Sea and Land in so much of the world as is already discovered, is equall and of the same extension.
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The Orbe of thicke and vaporous aire which inconpasses the Moone, makes the brighter parts of that Planet appeare bigger than in themselves they are; as I shall shew afterwards.
To the second it may be answered, that, that though the water be of a smooth superficies, and so may seeme most fit to reverberate the light, yet because ‘tis of a perspicuous nature,4 therefore the beames must sinke into it, and cannot so strongly and clearely be reflected. Sicut in speculo ubi plumbum abrasum fuerit, (saith Cardan) as in Looking-glasses where part of the lead is razed off, and nothing left behind to reverberate the image, the species must there passe through and not back againe; so it is where the beames penetrate and sinke into the substance of the body, there cannot be such an immediate and strong reflexion, as when they are beate back from the superficies, and therefore the Sunne causes a greater heate by farre upon the Land than upon the water. Now as for that experiment where it is sayd, that the waters have a greater brightnesse than the Land: I answer, ‘tis true onely there where they represent the image of the Sunne or some bright cloud, and not in other places, especially if wee looke upon them at any great distance, as is very plaine by common observation.
And ‘tis certaine that from any high mountaine the land dos appeare a great deale brighter than any lake or river.5
This may yet be farther illustrated by the similitude of a looking glasse hanging upon a wall in the Sun-shine, where, if the eye be not placed in the just line of reflexion from the glasse, tis manifest that the wall will bee of a brighter appearance than the glasse. True indeed in the line of reflexion, the light of the glasse is equall almost unto that which comes immediately from the Sunne it selfe; but now this is onely in one particular place and so is not like that brightnesse which wee discerne in the Moone, because this dos appeare equally in severall situations, like that of the wall which doe seeme bright as well from every place as from any one. And therefore the ruffnesse of the wall, or (as it is in the objection) the ruggednesse of our earth is so farre from being an hinderance of such a reflexion as there is from the Moone, that it is rather required as a necessary condition unto it. We may conceive that in every rough body there are, as it were innumerable superficies, disposed unto an innumerable diversitie of inclinations. Ita ut nullus sit locus,6 ad quem non pertingant plurimi radii reflexi a plurimis superficieculis, per omnem corporis scabri radiis luminosis percussi superficiem dispersis. So that there is not any place unto which there are not some beams reflected from these diverse superficies, in the severall parts of such a rugged body. But yet (as I said before) the earth dos receive a great part of its light by illumination, as wel as by reflexion.