REFRANGlBlLIfr of LIGttt. y§ 



We fhall fuppofe the attractive forces, which produce the re- 

 fractions of the red, green and violet light, to be reprefented 

 by the numbers eight, twelve and fixteen, in glafs ; fix, nine, 

 fourteen, in the metallic folution j fix, eleven, fourteen, in the 

 muriatic acid ; and fix, ten, fourteen, in a mixture of thefe two 

 fluids. The excefs of attraction of glafs for the red and violet 

 light is equal to two, whichfoever of the three fluids be em- 

 ployed. The refraction ofthefe two orders of rays will therefore 

 be the fame in all the three cafes. But the excefs of attraction 

 for the green light is equal to three, when the metallic folution 

 is ufed. and therefore the green light will be more refracted 

 than the red and violet, in this cafe. When the muriatic acid 

 is ufed, the excefs of attraction of glafs for the green light is 

 only one, and therefore the green light will now be lefs refract- 

 ed than the red and violet. We fhall next fuppofe the metallic 

 folution and the acid to adjoin each other. The attractions of 

 both thefe mediums, for the red light being fix, and for the 

 violet light fourteen, thefe two orders of rays will fufFer no 

 refraction in the confine of the two fluids, the difference of 

 their attractions being equal to nothing. 



But the attractive force of the metallic folution for the green 

 ray being only nine, and that of the muriatic acid for the fame 

 ray being eleven, the green light will be attracted towards the 

 muriatic acid with the force two ; and therefore the difference 

 between the refraction of the green light and the unrefracted 

 red and violet light which takes place in the confine of thefe 

 fluids, will greatly exceed ,the difference of refraction of the 

 green light, and equally refracted red and violet light, which is 

 produced in the confine of glafs and either of the fluids. 



Lastly, in a mixture of the two kinds of fluids, the attrac- 

 tion for the red. green and violet rays, being fix, ten and four- 

 teen, and that of the glafs, eight, twelve and fixteen, the excefs 

 of the attraction of the glafs for the green rays, is the fame 



K 2 which 



