38 JAMES CLEUK MAXWELL 



CHAPTER III. 



EARLY RESEARCHES. PHOFESSOK AT AHEHDEEX. 



FROM this time on Maxwell's life becomes a record 

 of his writings and discoveries. It will, however, 

 probably bo clearest to separate as far as possible 

 biographical details from a detailed account of his 

 scientific work, leaving this for consecutive treatment 

 in later chapters, and only alluding to it so far as 

 may prove necessary to explain references in his 

 letters. 



He continued in Cambridge till the Long Vacation 

 of 1854, reading Mill's " Logic." " I am experiencing 

 the effects of Mill," he writes, March 25th, 1854, " but 

 I take him slowly. I do not think him the last ot 

 his kind. I think more is wanted to bring the con- 

 nexion of sensation with science to light, and to show 

 what it is not" He also read Berkeley on "The 

 Theory of Vision" and " greatly admired it." 



About the same time ho devised an ophthalmo- 

 scope.* 



'* I have made an instrument for seeing into the eye 

 through the pupil. The difficulty is to throw the light in at 

 that small hole and look in at the same time ; but that 

 difficulty is overcome, and I can see a large part of tlio back 

 of the eye quite distinctly with the image of the candle on it. 

 People find no inconvenience in being examined, and I have 

 got dogs to sit quite still and keep their eyes steady. Dogs' 

 eyes are very beautiful behind a copper-coloured ground, with 



* " Life of J. C. Maxwell," p. 208. 



