Either the moon has light of its own, or it does not. If it has light of its own, why does it not shine without the aid of the sun? And if it does not have light of its own, necessity makes it a spherical mirror; and if it is a mirror, is it not proved in Perspective that the image of a luminous object will never be equal to the part of that mirror which is illuminated by that luminous body? And if this is so, as the figure here shows at r s, whence comes so great a quantity of splendour as the full moon has, which we see on the fifteenth day of the moon?

It is impossible that as much of the spherical mirror as the sun illuminates should shine over that same extent of the mirror, unless that mirror were wavy or covered in little globes. See here the sun illuminating the moon, a spherical mirror; and as much of it as the sun sees, so much of it does it make shine. Here it will be concluded that what shines of the moon is water like that of our seas and thus made wavy; and what of it does not shine are islands and dry land.

This demonstration of so many spherical bodies placed between the eye and the sun is made to show that, just as in each of those bodies the image of the sun is seen, so that image may be seen in each globosity of the waves of the sea; and as in many of these spheres many suns are seen, so in many waves many highlights are seen, which at a great distance each highlight by itself grows large to the eye, and, each wave doing likewise, the spaces between the waves come to be consumed; and for this reason it appears all one continuous sun in the many suns mirrored in the many waves, and the shadowy parts mixed with the luminous species make that splendour not as bright as that of the sun mirrored in those waves.