and its Use in Experiments of Polarization. 315 



that it is easy to conceive and to treat theoretically a resolution 

 of the light emerging- from any point of the crystal into two 

 pencils, one circularly-polarized and right-handed, and the other 

 also circularly-polarized but left-handed. To exhibit practically 

 the effects of this it is only necessary to contrive an analyzer 

 which shall wholly suppress right-handed circular light and wholly 

 transmit left-handed circular light, or vice versa. Another more 

 general resolution is into two elliptically-polarized pencils, one 

 right-handed and the other left-handed, the axes of the ellipses 

 having the same proportion, but the direction of the major axis 

 of one coinciding with that of the minor axis of the other. I am 

 not prepared to say whether or no any other resolution will be 

 found practicable. 



Now conceive the analyzer to be of the first new kind that 

 I have mentioned, namely to have the power of wholly suppress- 

 ing right-handed circular light and of wholly transmitting left- 

 handed circular light, or vice versa. I shall not consider the case 

 of plane-polarized light incident on the crystalline plate, because 

 the appearances are almost exactly the same (in theory as well as 

 in experiment) as when circularly polarized light is incident on 

 the crystal and the emergent light is analyzed by the common 

 analyzing plate: which case I have fully considered in former 

 memoirs in the Transactions of this Society, as well as in another 

 work. But let us consider the case of circularly polarized light 

 incident on the crystal, and after emergence analyzed by our new 

 analyzer. The first idea that strikes us in this combination is, 

 that there is nothing, except in the crystal, which has any respect 

 to sides. For the only incident light is circularly polarized: the 

 only light allowed to emerge is circularly polarized. The ap- 

 pearance therefore of the coloured rings, &c. must be such as 



KIt2 



