Others said that the moon was composed of parts more and less transparent, as if one part were like alabaster and another like crystal or glass, from which it would follow that the sun, striking with its rays the less transparent part, the light would remain on the surface, and so the denser part would remain illuminated while the transparent part would show the shadows of its dark depths; and thus the quality of the moon is composed. This opinion has pleased many philosophers, and especially Aristotle, and yet it is a false opinion, because in the different aspects that the moon and the sun often present to our eyes we see such spots vary, and at times they become dark and at times bright. They would become dark when the sun is in the west and the moon in the middle of the sky, for then the transparent concavities would take on the shadows up to the summits of the rims of such transparent hollows, because the sun could not drive its rays into the mouths of such concavities. And these would appear bright at the full moon, when the moon in the east looks upon the sun in the west; then the sun would illuminate even into the depths of such transparencies, and so, no shadows being generated, the moon would not show us at that time the aforesaid spots; and thus now more, now less, according to the changes of the sun with respect to the moon and of the moon with respect to our eyes, as I said above.