246 THE WORLD MACHINE 



consequences of his own studies and discoveries that thirteen or 

 fifteen years later, when the law of gravitation was announced, 

 great mathematician as he was, he pronounced it " absurd." 



But with the clearance of the sky, with the emptying of 

 space of any resisting medium to retard a planet's flight, with 

 the development of mechanical ideas, mechanical formulae, 

 measurements of motion, it is easy to understand how there 

 were other and younger men interested in the study of the 

 stars, eager to apply the new knowledge towards a solution of 

 the great problem. They would take up again the fascinating 

 suggestions thrown out by Gilbert of Colchester and by Kepler, 

 that there is a force acting outwards from the sun, holding the 

 planets in their orbits, and decreasing probably in direct pro- 

 portion to the distance from the centre of the system. 



These ideas had by no means been lost from view. That they 

 were in a sense current coin is evident enough from a passage 

 in the Novum Organum. Though Bacon had ignored Kepler as 

 he had ridiculed his own countryman, he borrows the ideas of 

 both, to refurbish them as his own : 



" Again, if there be any magnetic force which acts by sym- 

 pathy between the globe of the earth and heavy bodies, or 

 between that of the moon and the waters of the sea (as seems 

 most probable from the particular floods and ebbs which occur 

 twice in the month), or between the starry sphere and the 

 planets, by which they are summoned and raised to their 

 apogees, these must all operate at very great distances." 1 



As early as 1645 that is, a year after the appearance of 

 Descartes' Principia a French mathematician, Bouillaud, en- 

 deavours to refute Kepler's idea that such a force would de- 

 crease in simple proportion to the distance, and shows that it 

 would be as the square. But he seems to be as far as any from 

 connecting up such a force with common gravity. 



Borelli, in Pisa, attempts the problem. He is a disciple of 

 Galileo, one of the founders of the famous Accademia del 

 Cimento, which is the forerunner of the Royal Society, the 

 French Academy of Sciences, and all their like ; the author too 

 of the celebrated book in which the principles of mechanics are 

 first applied to animal motion. In his theory of the " Medician 

 planets," the satellites of Jupiter, not published until 1665 but 

 probably written long before, Borelli speculates upon " a natural 

 1 Novum Organum (1620). 



