150 GALILEO AND HIS JUDGES. 



the Earth. Then it struck him that however high 

 you ascend, even on the loftiest mountains, no sensible 

 diminution in this remarkable force takes place ; so, 

 he said to himself: why not as high as the Moon? 

 If so, perhaps she is retained in her orbit by this 

 very power. And again if so, what then? To 

 which question his active mind gave the just and 

 true answer, that it was probably one and the same 

 force that acted at the surface of the Earth, at the 

 distance of the Moon, and finally, as regulating the 

 action of the Sun on the planets. 



It seems that there was an error, which it is un- 

 necessary to explain in detail, in Newton's first 

 calculations ; but that when, after a lapse of time 

 and with the error corrected, he again returned to 

 them, he found the motion of the Moon to be 

 exactly accounted for by his theory. 



Again, in dealing with the complicated problem 

 of the action of the heavenly bodies one upon the 

 other, that is, when the disturbing force, for instance, 

 of a third body is brought to bear on the motions 

 of two others, although Hooke and others had as 

 a conjecture put forth the existence of such mutual 

 action, yet Newton was the first who thoroughly 

 grappled with it. 



The mutual attraction of matter, so far as things 

 terrestrial are concerned, had occurred to the in- 

 quiring intellect of Francis Bacon ; but it was left 

 for Newton to propound it as the great principle 

 that governs the physical universe. 



