PHYSICAL AND LITERARY. 53 



to his diftance from the fun; Ught take5 

 about forty one minutes of time in paffing 

 from him to the earth : therefore the Uft 

 violet light which a fateUite refle(Ets, before its 

 total immeriion Into the (hadow of Jupiter, 

 ought to continue. to affe£t the eye for a 77ih 

 part of 41', or 32", after the red reflected 

 at the fame time is gone : that is, A fatehite, 

 feen frorn the earth, ought to change its 

 colour above half a minute before its total 

 immerfion from white to a livid green ifh 

 colour, thence into blue, and at laft evanifh 

 in violet. I need fcarcely obferve, that the 

 lanie phenomenon fhould take place in the 

 time of emerfion, by a contrary fucceflion 

 pf colours, beginning with red .^nd ending ii> 

 white. .rr . " 



50. If this phenomenon fhould be adually 

 perceived by aftronomers, we fhall haVe a 

 fufficient dlred proof of the different velo- 

 cities of the coloured rays j for I fee not tp 

 what other caufe the phanojne?wn could be 

 rationally afcribed: If it be not, we may 

 conclude that rays of all colours are emitted 

 ^pd reflefted with one common velocity. 



SECT. 



