202 Literary and Philosophical Society, 



Gough told him that he might go to the growing city of 

 Manchester and be a professor practically in a new college, 

 the Manchester Academy (Appendix B.). He arrived in 1 793 

 with his * Meteorological Observation and Essays,' ready or 

 almost ready for publication. They were begun in 1788. 



The works of Dalton are numerous, and a list need not 

 be given here, as one may be found in the fuller accounts 

 of his life. We shall look only on some of his greatest 

 feats. He entered this Society as a professed mathematician ; 

 but this department ceased to be specially interesting to 

 him, and the attention he had given to meteorology was such 

 that hitherto his only long treatise was on that subject, and 

 it was his first separate work published. His first paper 

 printed in the memoirs, ' Extraordinary Facts Relating to 

 the Vision of Colours,' was out of the direct course of his 

 studies, but has been the foundation of a most valuable 

 series of inquiries. The condition of vision analogous to 

 Dalton's has been of late called colour-blindness, a plain 

 and simple expression for the extreme condition, but by no 

 means expressing the varieties. As the writer has else- 

 where said, ' It is probable that there are many gradations, 

 beginning with deficient colour sight and ending in dichromic, 

 or perhaps monochromic or achromic vision, or true colour- 

 blindness.' Dalton was short-sighted, but had powerful 

 eyes that never wearied. Without this first discovery of 

 Dalton's, railway night-signals would be seen erroneously 

 in nearly ten cases out of a hundred, and one out of ten 

 engine-drivers might be misled at every coloured lamp along 

 the lines of rail. This first gift of Dalton to the Society is 

 now a matter of national importance, and we may say that 

 it is of value to all nations in which railways exist and to 

 all who are interested in navigation, leaving little behind of 



