EBB AND FLOW. 199 



Now this, it seems, may be taken as a probable reason for 

 supposing that that motion is not limited to the heavens; 

 because it prevails and is in force through so great a depth 

 of heaven as lies between the starry heaven and the moon, 

 (a space much more extensive than that between the moon 

 and the earth), with a regular diminution ; so that it is 

 probable that nature does not at any point abruptly break 

 oft a harmonious motion of this kind, diffused through such 

 vast spheres and gradually lessening. And that this is 

 so in the heavenly bodies is evinced by two inconsistencies, 

 which follow from the opposite hypothesis. For since 

 the planets visibly perform a diurnal motion, unless we are 

 to suppose that motion natural and self-moved in all the 

 planets, we must unavoidably have recourse for an expla 

 nation either to the supposition of the primum mobile, 

 which is evidently opposed to nature ; or to the rotation of 

 the earth, which is a notion extravagant enough, if we look 

 to the methods of nature. Therefore the motion exists in 

 the heavenly bodies. And, quitting heaven, that motion is 

 most distinctly visible in the inferior comets ; which, though 

 lower than the orb of the rnoon, evidently move from east 

 to west. For though they have their solitary and eccen 

 tric motions, yet in performing them they for a time have 

 a common movement, and are borne along with the motion 

 of the ether, and with the same conversion : but in the 

 tropics they are not generally so confined, nor move in the 

 regular course, but sometimes straggle towards the poles, 

 yet nevertheless pursue their rotatory motion from east to 

 west. And thus this motion, though it suffers great dimi 

 nution, since the nearer it descends towards earth the con 

 version is performed in smaller circles, and more slowly, 

 still remains powerful, so as to traverse great distances 

 in a short time. For these comets are carried round the 

 whole circumference, both of the earth and the lower at 

 mosphere, in the space of twenty-four hours, with an ex 

 cess of one or two hours more. But after, by a continued 

 descent, it has reached these regions upon which the earth 

 acts, this motion, not only by the communication of the 

 earth s nature and influence, which represses and lowers 

 circular motion, but also by a substantial immission of the 

 particles of its matter, by means of vapours and gross ex 

 halations, becomes infinitely relaxed, and almost falls off, 

 yet it is not therefore wholly annihilated or ceases, but 

 remains feeble and verging to imperceptible. For mariners 

 now begin to confess that between the tropics, where, in 



