PROFESSOR AT HEIDELBERG 243 



make an objective imitation of the subjective phenomena of the 

 eye, such as the irradiation caused by its transparent but not 

 perfectly clear media ; while most of all, it is the harmony of 

 colours that comes into question, since the reciprocal relations 

 of the colours of a picture have much to do with the aesthetic 

 enjoyment of it, and even strong colours can convey expression 

 (in the artistic sense) of the most delicate alteration or illumi- 

 nation. 



i What is the effect to be produced by a work of art, using 

 this word in its highest sense ? It should excite and arrest our 

 attention, awaken a rich train of sleeping associations and cor- 

 related feelings into activity, and direct them to a common end, 

 in order to unite all the features of an ideal type which are 

 lying scattered in our memory in isolated fragments, overgrown 

 by a confused and fortuitous mass of ideas into a vivid con- 

 ception. We can only explain the frequent preponderance of 

 art over reality in the human mind, by saying that impressions 

 of the latter are always mingled with something that disturbs, 

 distracts, and injures us, while in art the elements which are to 

 produce the desired impression are gathered together and 

 allowed to act without restraint. The force of the impression 

 will, however, undoubtedly be stronger in proportion to the 

 depth, refinement, and truth to nature of the sensory impression 

 which is to arouse the series of images and the emotions 

 associated therewith. Its effect must be prompt, certain, un- 

 equivocal, and exact, if it is to call up a vivid and powerful 

 impression/ 



After the publication of his Theory of Sensations of Tone and 

 Physiological Optics, Helmholtz gave himself up more and more 

 to problems in mathematical physics, and pure mathematics; 

 the few physiological papers that he published were in con- 

 nexion with his earliest work on the physiology of nerve, which 

 had been pushed into the background of late years owing to the 

 extraordinary output of his new work. He was so exhausted 

 by his labours in physiological optics that he found himself 

 reluctantly obliged to forgo the pressing invitation of Roscoe 

 to attend the Meeting of the British Association, and set off in 

 the autumn holidays of 1866 with his wife for Switzerland, where 

 he met the Kirchhoffs and Bunsen. After a short journey 

 through North Italy he returned a few weeks later to Heidelberg, 



R 2 



