TJfEOKY OF THE FIRMAMENT. / 



and that motion in the constellated firmament is perfect 

 and entire, as well as to a just measure of time, as by a 

 full restoration of place; but, inasmuch as that motion 

 recedes from the summit of the heavens, insomuch does 

 it become more imperfect, with reference to its slowness as 

 well as its aberration from a circular motion. And, first, 

 we must speak distinctly of that slowness. We affirm, 

 that the diurnal motion of Saturn is too slow to carry it 

 round, and restore it to the same point in twenty-four 

 hours ; but that the starry firmament is carried on quicker, 

 and outstrips Saturn by such an excess, as, in as many 

 days as complete thirty years, would agree with a whole 

 circuit of the heavens. The same is to be said of the rest 

 of the planets, according to the difference of the periodic 

 time of each planet; so that the diurnal motion of the 

 starry firmament (in that same period, without any regard 

 to the magnitude of the circle) is nearly by one hour 

 swifter, than the diurnal motion of the moon ; for, if the 

 moon could complete its revolution in twenty-four days, 

 then that excess would be one whole hour; wherefore 

 that much talked of motion, in an opposite and contrary 

 direction from west to east, which is attributed as pecu 

 liar to the planets, is not true, but only apparent, from the 

 outstripping of the starry firmament toward the west, and 

 the leaving behind of the planets toward the east, which 

 being granted, it is evident that the velocity of that cos- 

 mical motion, by an unperturbed law of nature, as it des 

 cends, decreases, so that the nearer each planet approaches 

 the earth, the slower it moves ; whereas the received opi 

 nion overthrows and turns upside down that law ; and by 

 attributing a motion of their own to the planets, falls into 

 the absurdity, that the planets, the nearer they are to the 

 earth (which is, naturally, the place of rest), in that ratio 

 have their celerity increased ; which astronomers, in the 

 most trifling and unsuccessful manner, attempt to excuse, 

 by a relaxation of the force of the primum mobile. But 

 it it seem to any one a matter of wonder, that, in spaces 

 so vast as interpose between the starry firmament and the 

 moon, that motion should gradually decrease by portions 

 so small, by less, to wit, than one hour, which is the 

 twenty-fourth part of the diurnal motion ; it subsides when 

 we consider that each planet, the nearer it is to the earth, 

 completes lesser circles, revolving in a shorter circuit; so 

 that, the decrement of the size of the circle being added to the 



