288 Mb KELLAND, ON THE MOTION OF A SYSTEM OF PARTICLES. 



and Lit^ht, should not have undertaken observations on substances 

 such as to compare the gradations in the affection of the latter with 

 those of the former. 



The nature of the investigation I have here attempted must plead 

 my excuse for having been rather discursive. My object has been so 

 to consider the constitution of the atmosphere, that one single hypo- 

 thesis shall suffice as a key by which to proceed to the examination 

 and explanation of the varied phenomena which present themselves to 

 our notice. I do not presume to suppose that I have succeeded, but 

 the necessity of keeping the different kinds of phenomena in as in- 

 timate connexion as possible, has induced me to offer the above to 

 the notice of the Society. 



ERRATUM. 



In Part I, page 179, replace the seven lines from the bottom by the ibllowing ; 



D" = 2i42. =i — s sm' — ^ 



)• ,\ 



V = ~^r 2 . ^ ir sin 



(■' r' \ 



and at the top of the following page, read 



Sin" sm' 



2t« L. = sr". —. 



