48 Mr. S. P. Thompson on the Chvonuitic Aberration 



I consider it a very fortunate circumstance that observers 

 have met with facts so abnormal in appearance, because these 

 latter give a valuable support to my theory. In reality, the 



. cZT 



character of the maximum or minimum of the expression S -j- 



for particular values of S and t necessarily involves two effects 

 of contrary signs on this side and on that of this particular 

 state of the body. It hence follows that, if physicists had not 

 already noted the striking irregularities of which I have spoken, 

 my theory might have instigated their discovery. 



IV. If the consequences which I have deduced from my 

 formula be verified not only by the facts already known, but 

 moreover by the experiments which it may suggest, it can be 

 foreseen of what importance this theory will be in thermody- 

 namics, in which the state of a body is at present regarded as 

 determined when the volume, the temperature, and the pres- 

 sure supported by the body are given. When a liquid, and 

 very probably also when a solid or a gaseous body, is in ques- 

 tion, it will be absolutely necessarj^ to take account of the po- 

 tential energy which prevails in all the bounding surfaces. 



The investigation of this question will be able to be carried 

 on step by step, in proportion as facts shall have brought more 

 confirmation to the calculations which have served me as a 

 basis for the deduction of the various consequences enunciated 

 in my two communications. 



V. I should now have to investigate what are the electrical 

 phenomena corresponding to the various developments of heat 

 which have been in question in this note ; but this is too w^ide 

 a subject for any thing less than a special treatise. I will, for 

 the present, only say that, from the numerous bibliographical 

 researches which I have already instituted, I hope to find for 

 my theory a confirmation as complete in the domain of elec- 

 tricity as in that of heat. 



VI. On the Chromatic Aberration of the Eye in relation to 

 the Perception of Distance. By SiLVANUS P. Thompson, 

 B,A, B.Sc^ 



1. rr^HE experimental researches of Wollaston, Arago, 

 J- Fraunhofer, Young, Matthiesen, Brewster, Miiller, 

 and Helmholtz have left no doubt that the eye has the defect 

 of chromatic aberration. Pays of light of dissimilar colour, 

 starting in the same direction from any luminous point and 



* Communicated by the Aiitlior, having been read before the Physical 

 Society, May 12, 1877. 



