24 CLASSICS OF MODERN SCIENCE 

 to those who remain on the shores gradually to sink and at last still 

 sinking to disappear. It is clear that the water also according to its 

 nature continually presses like the earth downward, and does not 

 rise above its banks higher than its convexity permits. So the land 

 extends above the ocean as much as the land happens to be higher. 



WHETHER THE EARTH HAS A CIRCULAR MOTION, AND CONCERNING 



THE LOCATION OF THE EARTH 



As it has been already shown that the earth has the form of a 

 sphere, we must consider whether a movement also coincides with this 

 form, and what place the earth holds in the universe. Without this 

 there will be no secure results to be obtained in regard to the heavenly 

 phenomena. The great majority of authors of course agree that the 

 earth stands still in the center of the universe, and consider it incon- 

 ceivable and ridiculous to suppose the opposite. But if the matter is 

 carefully weighed it will be seen that the question is not yet settled 

 and therefore by no means to be regarded lightly. Every change of 

 place which is observed is due, namely, to a movement of the observed 

 object or of the observer, or to movements of both, naturally in differ- 

 ent directions, for if the observed object and the observer move in the 

 same manner and in the same direction no movement will be seen. 

 Now it is from the earth that the revolution of the heavens is observed 

 and it is produced for our eyes. Therefore if the earth undergoes 

 no movement this movement must take place in everything outside of 

 the earth, but in the opposite direction than if everything on the earth 

 moved, and of this kind is the daily revolution. So this appears to 

 affect the whole universe, that is, everything outside the earth with 

 the single exception of the earth itself. If, however, one should admit 

 that this movement was not peculiar to the heavens, but that the earth 

 revolved from west to east, and if this was carefully considered in 

 regard to the apparent rising and setting of the sun, the moon and the 

 stars, it would be discovered that this was the real situation. Since 

 the sky, which contains and shelters all things, is the common seat of 

 all things, it is not easy to understand why motion should not be 

 ascribed rather to the thing contained than to the containing, to the 

 located rather than to the location. From this supposition follows an- 

 other question of no less importance, concerning the place of the 



