



B. Vision, Light, and Colours 



Interesting proof of the range of 

 Michell's studies in natural philosophy 

 and of the singularly large-minded gene- 

 rosity with which he freely communi- 

 cated to other fellow-workers the results 

 of his own unpublished researches is 

 furnished by the record of his association 

 with Joseph Priestley. That illustrious 

 philosopher became minister of Mill Hill 

 Chapel, Leeds, in 1767, the same year 

 that saw John Michell settled in the 

 rectory of Thornhill. He had already 

 made known his growing heterodoxy, 

 but he had also shown such striking 

 powers in scientific discussion, particu- 

 larly in regard to electricity, that the 

 Royal Society had already in 1766 elected 

 him one of its body. Leeds and Thorn- 

 hill being only a few miles apart, it was 

 natural that the two men of science 

 should become acquainted with each 

 other. In these days it said much for the 

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