322 Professor Airy on a new Analyzer, &fc. 



zation : and therefore in both cases the appearance will be that 

 of patches or curves extending continuously through all the parts 

 where the gain of one ray upon the other is a constant quantity. 



In the former part of this paper I have alluded to an analyzer 

 of a more general kind, namely one in which the light is separated 

 into two elliptically-polarized rays. This is constructed by plac- 

 ing the plate of mica with its principal plane inclined to that 

 of reflection at the unsilvered glass by an angle different from 

 45". The investigation of its effects is not more difficult than that 

 above, but is rather longer, and its results will hardly justify its in- 

 sertion. I will only remark that, with the apparatus which I have 

 supposed employed for the experiment above, if the Fresnel's 

 rhomb or mica by which the incident light is made circularly- 

 polarized, and the mica by which the new analyzation is effected, 

 are turned the same way (leaving the glass reflector unmoved) 

 the continuity of the rings is not interrupted, but a part of the 

 image is seen to grow darker and darker; and when both are 

 turned 45°, this dark part becomes the black brush. This sup- 

 poses the planes of original polarization and of reflection at the 

 glass to be at right angles; but if they are parallel the change 

 is of the opposite kind, and the bright brushes are finally pro- 

 duced. 



G. B. AIRY. 



Observatory, 



Jan. 19, 1832. 



