152 HISTORY OF PHYSICAL ASTRONOMY. 



printed in 1600, has only some vague notions that 

 the magnetic virtue of the earth in some way deter- 

 mines the direction of the earth's axis, the rate of 

 its diurnal rotation, and that of the revolution of 

 the moon about it 20 . He died in 1603, and, in his 

 posthumous work, already mentioned, (De Mundo 

 nostro SuUunari Philosophia nova., 1651,) we have 

 already a more distinct statement of the attraction 

 of one body by another 21 . " The force which ema- 

 nates from the moon reaches to the earth, and, in 

 like manner, the magnetic virtue of the earth per- 

 vades the region of the moon : both correspond and 

 conspire by the joint action of both, according to a 

 proportion and conformity of motions : but the earth 

 has more effect, in consequence of its superior mass' 

 the earth attracts and repels the moon, and the 

 moon, within certain limits, the earth ; not so as to 

 make the bodies come together, as magnetic bodies 

 do, but so that they may go on in a continuous 

 course." Though this phraseology is capable of 

 representing a good deal of the truth, it does not 

 appear to have been connected, in the author's 

 mind, with any very definite notions of mechanical 

 action in detail. We may probably say the same of 

 Milton's language : 



What if the sun 



Be center to the world; and other stars, 

 By his attractive virtue and their own 

 Incited, dance about him various rounds ? 



Par. Lay/, B. viii. 



20 Lib. vi. cap. 6, 7- Sl lb. ii. c. 19. 



