CHAPTER VII 



HELMHOLTZ IN KONIGSBERG THE OPHTHALMOSCOPE 



T_N_.i85l Helmholtz conferred an inestimable benefit 

 "1 on humanity, became famous far beyond the 

 circle of his scientific friends, and handed his name 

 on to posterity by the invention of the ophthalmo- 

 scope. Had he done little else in his long lifetime, his 

 name would never be forgotten ; and yet the inven- 

 tion of this instrument took its origin not in any 

 profound investigation, but in the desire to exhibit 

 a physiological phenomenon to his students. It was 

 characteristic, however, of his mind that he was ever 

 receptive of new impressions, and when an idea 

 occurred to him, his powers were brought persistently 

 to bear upon it, and if it involved a problem, he had 

 no rest until it was solved. The invention of the 

 ophthalmoscope is a striking example, also, of his 

 singular power of combining the theoretical with the 

 practical in his daily life ; and he could turn his mind 

 from the contemplation of the mathematical expres- 

 sions of the law of the conservation of energy, trac- 

 ing in his imagination its tremendous consequences, 

 to devising the best method of illuminating the eye. 

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