284 HERMANN VON HELMHOLTZ: 



an hour of perfect bodily repose and quiet comfort was 

 necessary before the good ideas came. They often 

 came actually in the morning on waking, as expressed 

 in Goethe's words which I have quoted, and as Gauss 

 also has remarked. 1 But, as I have stated in Heidel- 

 berg, they were usually apt to come when comfortably 

 ascending woody hills in sunny weather. The smallest 

 quantity of alcoholic drink seemed to frighten them 

 away. 



Such moments of fruitful thought were indeed very 

 delightful, but not so the reverse, when the redeeming 

 ideas did not come. For weeks or months I was gnaw- 

 ing at such a question until in my mind I was 



Like to a beast upon a barren heath 

 Dragged in a circle by an evil spirit, 

 While all around are pleasant pastures green. 



And, lastly, it was often a sharp attack of headache 

 which released me from this strain, and set me free for 

 other interests. 



I have entered upon still another region to which I 

 was led by investigation on perception and observation 

 of the senses, namely, the theory of cognition. Just 

 as a physicist has to examine the telescope and galva- 

 nometer with which he is working ; has to get a clear 

 conception of what he can attain with them, and how 



1 Gauss, Wcrke, vol. v. p. 609. * The law of induction discovered 

 Jan. 23, 1835, at 7 A.M., before rising.' 



