Plutarch De Facie Quae in orbe Lunae Apparet 21

[21] As soon as Lucius had said these things, Pharnaces and Apollonides ran both together upon him, to oppugn and refute his discourse; and then Apollonides giving him way, Pharnaces said: This it is that principally shows the moon to be a star and of a fiery nature, that in her eclipses she is not wholly obscured and disappearing, but shows herself with a certain coal-resembling color, terrible to the sight, yet such as is proper to her.

As for Apollonides, he insisted much in opposition to the word shadow, saying, that the mathematicians always give that name to the place which is not enlightened, and that heaven admits no shadow.

To this I thus answered: This instance is rather alleged obstinately against the name, than naturally or mathematically against the thing. For if one will not call the place obfuscated by the opposition of the earth a shadow, but a place deprived of light, yet be it what it will, you must of necessity confess that the moon being there becomes obscure; and every way, said I, it is a folly to deny that the shadow of the earth reaches thither from whence the shadow of the moon, falling upon our sight here on earth, causes the eclipse of the sun. And therefore I now address myself to you, Pharnaces; for this coal-like and burnt color of the moon, which you affirm to be proper to her, belongs to a body that has thickness and depth. For there is not wont to remain any relic, mark, or print of flame in a body that is rare, nor can a coal be made where there is not a solid body which may receive into it the heat of the fire; as Homer himself shows in a certain passage, where he says, For the coal seems not properly a fire, but a body enkindled and altered by the fire, which stays and remains in a solid firmly rooted mass; and whereas flames are the setting on fire and fluxions of a nutriment and matter, which is of a rare substance, and by reason of its weakness quickly dissolved and consumed; so that there could not be any more evident and plain argument to demonstrate that the moon is solid and earthly, than if ’her proper color were that of a coal. But it is not so, my friend Pharnaces; but in her eclipses she diversely changes her colors, which the mathematicians, determining with respect to the time and hour, thus distinguish. If she is eclipsed in the evening, she appears horribly black until the middle of the fourth hour of the night; if about midnight, she sends forth this reddish and fire-resembling color, and after the middle of the eighth hour, the redness disappears; and finally, if about the dawning of the morning, she takes a blue or grayish color; which is the cause why she is by the poets, and particularly by Empedocles, called Glaucopis.

Since then they clearly see that the moon changes into so many colors in the shadow, they do ill to attribute to her only that of a burning coal, which may be said to be less proper to her than any other, being only a small remnant and semblance of light, appearing and shining through a shadow, her own proper color being black and earthy. And since that here below, red and purple garments, and rivers and lakes, which receive the rays of the sun, cause neighboring shady places to take the same appearances of colors and to be illuminated by them, casting and sending back by reason of reflections several rebated splendors; what wonder is it if a copious flux of shadow, falling as it were into an immense celestial sea of light, not steady and quiet, but agitated by innumerable stars, and besides admitting several mixtures and mutations in itself, takes from the moon the impression sometimes of one color, sometimes of another, and sends them hither to us? For it is not to be denied but that a star of fire cannot appear in a shadow black, gray, or violet; but there are seen upon hills, plains, and seas, several various resemblances of colors, caused by the reflection of the sun, which are the very tinctures that brightness mixed with shadows and mists, as if it were with painters’ colors, brings upon them. And as for the tincture or colors of the sea, Homer has indeed in some sort endeavored to name and express them, when he sometimes terms the sea violet-colored or red as wine, at other times the waves purple, and again the sea blue, and the calm white. As for the diversities of tinctures and colors appearing upon the earth, he has, I suppose, omitted them, because they are in number infinite. Now it is not probable that the moon has but one superficies all plain and even, as the sea; but rather that of its nature it principally resembles the earth, of which old Socrates in Plato seemed to mythologize at his pleasure; whether it were, that under covert and enigmatical speeches he meant it of the moon, or whether he spake it of some other. For it is neither incredible nor wonderful, if the moon, having in herself nothing corrupt or muddy, but enjoying a pure and clear light from heaven, and being full of heat, not of a burning and furious fire, but of such as is mild and harmless, has in her places admirably fair and pleasant, resplendent mountains, purple-colored cinctures or zones, and store of gold and silver, not dispersed here and there within her bowels, but flourishing in great abundance on the superficies of her plains, or spread all over her smooth hills and mountains.

And if the sight of all these things comes to us through a shadow, sometimes in one manner and sometimes in another, by reason of the diversity and different change of the ambient air, the moon does not therefore lose the venerable persuasion that is had of her, or the reputation of divinity; being esteemed by men a heavenly earth, or rather (as the Stoics say) a troubled, thick, and dreggish fire. For even the fire itself is honored with barbarian honors among the Assyrians and Medes, who through fear serve and adore such things as are hurtful, hallowing them even above such things as are of themselves indeed holy and honorable. But the very name of the earth is truly dear and venerable to every Greek, and there is through all Greece a custom received of adoring and revering it, as much as any of the Gods. And we are very far from thinking that the moon, which we hold to be a heavenly earth, is a body without soul and spirit, exempt and deprived of all that is to be offered to the Gods. For both by law we yield her recompenses and thanksgivings, for that we receive of her and by nature we adore what we acknowledge to be of a more excellent virtue and a more honorable power; and therefore we do not think that we offend in supposing the moon to be earth.

Now as to the face which appears in her, as this earth on which we are has in it many great sinuosities and valleys, so it is probable that the moon also lies open, and is cleft with many deep caves and ruptures, in which there is water or very obscure air, to the bottom of which the sun cannot reach or penetrate, but failing there, sends back a dissipated reflection to us here below.