REFRANGIBILITY of LIGHT. n6 
We fhall fuppofe the attra@tive 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; 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 refra¢t- 
ed than the red and violet. We fhall next fuppofe the metallic 
folution and the acid to adjoin each other. The attraétions of 
both thefe mediums, for the red light being fix, and for the’ 
violet light fourteen, thefe two orders of rays will fuffer no 
refraGtion in the confine of the two fluids, the difference of 
their attractions being equal to nothing. 
Bur 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 attraéted towards the 
muriatic acid with the force two; and therefore the difference 
between the refraction of the green light and the unrefraéted 
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 
; Kgs which 
