For, as the heaven is everlasting revolving, in a circle without any cessation or interruption, it follows of necessity that each of the hemispheres must every day be in a different position from that which it was in the day before, everything being turned upside down as far as appearance goes, at least; for, in point of fact, there is no such thing as any uppermost or undermost in a spherical figure. And this expression is only used with reference to our own formation and position; that which is over our head being called uppermost, and that which is in the opposite direction being called undermost.