212 JAMES CLERK MAXWELL. [CHAP. VII. 



Philosophical here. I am to let them see the tricks on 

 Monday evening, and I have been there preparing their 

 experiments in the gas-light. There is to be a meeting in 

 my rooms to-night to discuss Adam Smith's "Theory of Moral 

 Sentiments," so I must clear up my litter presently. I am 

 working away at electricity again, and have been working 

 my way into the views of heavy German writers. It takes 

 a long time to reduce to order all the notions one gets from 

 these men, but I hope to see my way through the subject 

 and arrive at something intelligible in the way of a theory. 



Trin. Coll., 15th May 1*55. 



The colour trick came off on Monday, 7th. I had the 

 proof sheets of my paper, and was going to read ; but I 

 changed my mind and talked instead, which was more to the 

 purpose. There were sundry men who thought that Blue 

 and Yellow make Green, so I had to undeceive them. I 

 have got Hay's book of colours out of the Univ. Library, 

 and am working through the specimens, matching them 

 with the top. I have a new trick of stretching the string 

 horizontally above the top, so as to touch the upper part of 

 the axis. The motion of the axis sets the string a- vibrating 

 in the same time with the revolutions of the top, and the 

 colours are seen in the haze produced by the vibration. 

 Thomson has been spinning the top, and he finds my dia- 

 gram of colours agrees with his experiments, but he doubts 

 about browns what is their composition. I have got col- 

 cothar brown, and can make white with it, and blue and 

 green ; also, by mixing red with a little blue and green and 

 a great deal of black, I can match colcothar exactly. 



I have been perfecting my instrument for looking into 

 the eye. Ware has a little beast like old Ask, 1 which sits 

 quite steady and seems to like being looked at, and I have 

 got several men who have large pupils and do not wish to 

 let me look in. I have seen the image of the candle dis- 

 tinctly in all the eyes I have tried, and the veins of the 



1 Above, p. 57. 



