INDUCTIVE EPOCH OF NEWTON. 160 



entific operation then recently completed, gave the 

 explanation at once. He had been mistaken in the 

 magnitude of the earth, and consequently in the 

 distance of the moon, which is determined by mea- 

 surements of which the earth's radius is the base. 

 He had taken the common estimate, current among 

 geographers and seamen, that sixty English miles 

 are contained in one degree of latitude. But Picart, 

 in 1670, had measured the length of a certain por- 

 tion of the meridian in France, with far greater 

 accuracy than had yet been attained; and this 

 measure enabled Newton to repeat his calculations 

 with these amended data. We may imagine the 

 strong curiosity which he must have felt as to the 

 result of these calculations. According to the 

 account which is given by Robison 6 , "He went 

 home, took out his old papers, and resumed his 

 calculations. As they drew to a close, he was so 

 much agitated that he was obliged to desire a friend 

 to finish them." His former conjecture was now 

 found to agree with the phenomena to a remarkable 

 degree of precision. This conclusion, thus coming 

 after long doubts and delays, and falling in with 

 the other results of mechanical calculation for the 

 solar system, gave a stamp from that moment to his 

 opinions, and through him to those of the whole 

 philosophical world (F). 



It does not appear, I think, that before Newton, 



1 Robison, Phys. Aslr. Art. 197- I do not know the 

 authority for this anecdote. 



