NICOLAUS COPERNICUS 27 



belong to that region and which rise and set like other stars. We may 

 suppose that part of the atmosphere, because of its great distance 

 from the earth, has become free from the earthly motion. So the 

 atmosphere which lies close to the earth and all things floating in 

 it would appear to remain still, unless driven here and there by the 

 wind or some other outside force, which chance may bring into play ; 

 for how is the wind in the air different from the current in the sea? 

 We must admit that the motion of things rising and falling in the air 

 is in relation to the universe a double one, being always made up of 

 a rectilinear and a circular movement. Since that which seeks of its 

 own weight to fall is essentially earthy, so there is no doubt that these 

 follow the same natural law as their whole; and it results from the 

 same principle that those things which pertain to fire are forcibly 

 driven on high. Earthly fire is nourished with earthly stuff, and it is 

 said that the flame is only burning smoke. But the peculiarity of the 

 fire consists in this that it expands whatever it seizes upon, and it car- 

 ries this out so consistently that it can in no way and by no machinery 

 be prevented from breaking its bonds and completing its work. The 

 expanding motion, however, is directed from the center outward; 

 therefore if any earthly material is ignited it moves upward. So to 

 each single body belongs a single motion, and this is evinced prefer- 

 ably in a circular direction as long as the single body remains in its 

 natural place and its entirety. In this position the movement is the 

 circular movement which as far as the body itself is concerned is as 

 if it did not occur. The rectilinear motion, however, seizes upon 

 those bodies which have wandered or have been driven from their nat- 

 ural position or have been in any way disturbed. Nothing is so much 

 opposed to the order and form of the world as the displacement of one 

 of its parts. Rectilinear motion takes place only when objects are not 

 properly related, and are not complete according to their nature because 

 they have separated from their whole and have lost their unity. More- 

 over, objects which have been driven outward or away, leaving out 

 of consideration the circular motion, do not obey a single, simple and 

 regular motion, since they cannot be controlled simply by their light- 

 ness or by the force of their weight, and if in falling they have at first 

 a slow movement the rapidity of the motion increases as they fall, while 

 in the case of earthly fire which is forced upwards — and we have no 

 means of knowing any other kind of fire — we will see that its motion 



