192 HISTORY OF PHYSICAL ASTRONOMY. 



therefore, how it was that Newton could not admit 

 that there was any difference between himself and 

 other men, except in his possession of such habits 

 as we have mentioned, perseverance and vigilance. 

 When he was asked how he made his discoveries, 

 he answered, " by always thinking about them ;" 

 and at another time he declared that if he had done 

 anything, it was due to nothing but industry and 

 patient thought : " I keep the subject of my inquiry 

 constantly before me, and wait till the first dawning 

 opens gradually, by little and little, into a full and 

 clear light." No better account can be given of the 

 nature of the mental effort which gives to the phi- 

 losopher the full benefit of his powers; but the 

 natural powers of men's minds are not on that 

 account the less different. There are many who 

 might wait through ages of darkness without being 

 visited by any dawn. 



The habit to which Newton thus, in some sense, 

 owed his discoveries, this constant attention to the 

 rising thought, and developement of its results in 

 every direction, necessarily engaged and absorbed 

 his spirit, and made him inattentive and almost 

 insensible to external impressions and common im- 

 pulses. The stories which are told of his extreme 

 absence of mind, probably refer to the two years 

 during which he was composing his Principia, and 

 thus following out a train of reasoning the most 

 fertile, the most complex, and the most important, 

 which any philosopher had ever had to deal with. 



