150 HISTORY OF PHYSICAL ASTRONOMY. 



to a later period of our history ; to the reception, 

 not to the prelude, of the Newtonian theory. 



(Borelli.) In Italy, Holland, and England, ma- 

 thematicians appear to have looked much more 

 steadily at the problem of the celestial motions, by 

 the light which the discovery of the real laws of 

 motion threw upon it. In Borelli's Theories of the 

 Medicean Planets, printed at Florence in 1666, we 

 have already a conception of the nature of central 

 action, in which true notions begin to appear. The 

 attraction of a body upon another which revolves 

 about it is spoken of, and likened to magnetic 

 action; not converting the attracting force into a 

 transverse force, according to the erroneous views 

 of Kepler, but taking it as a tendency of the bodies 

 to meet. "It is manifest," says he 17 , "that every 

 planet and satellite revolves round some principal 

 globe of the universe as a fountain of virtue, which 

 so draws and holds them, that they cannot by any 

 means be separated from it, but are compelled to 

 follow it wherever it goes, in constant and continu- 

 ous revolutions." And, further on, he describes 18 

 the nature of the action, as a matter of conjecture 

 indeed, but with remarkable correctness 19 . "We 

 shall account for these motions by supposing, that 

 which can hardly be denied, that the planets have a 

 certain natural appetite for uniting themselves with 

 the globe round which they revolve, and that they 

 really tend, with all their efforts, to approach to 

 17 Cap. 2. 18 Ib. 11. l9 p. 47. 



