AN AUTOBIOGBAPHICAL SKETCH. 233 



Bat who can count or measure such mental flashes ? 

 Who can follow the hidden tracts by which conceptions 

 are connected ? 



That which man had never known, 

 Or had not thought out, 

 Through the labyrinth of mind 

 Wanders in the night. 



I must say that those regions, in which we have not 

 to rely on lucky accidents and ideas, have always been 

 most agreeable to me, as fields of work. 



But, as I have often been in the unpleasant position 

 of having to wait for lucky ideas, ITiave had some ex- 

 perience as to when and where they came to me, which 

 will perhaps be useful to others. They often steal into 

 the line of thought without their importance being at 

 first understood ; then afterwards some accidental cir- 

 cumstance shows how and under what conditions they 

 have originated ; they are present, otherwise, without 

 our knowing whence they came. In other cases they 

 occur suddenly, without exertion, like an inspiration. 

 As far as my experience goes, they never came at the 

 desk or to a tired brain. I have always so turned my 

 problem about in all directions that I could see in my 

 mind its turns and complications, and run through them 

 freely without writing them down. But to reach that 

 stage was not usually possible without long preliminary 

 work. Then, after the fatigue from this had passed away, 



