Second Series. — Circular Polarization. 469 



or — 45° to the plane of reflection, and the analyzing plate was 

 placed in the parallel and rectangular positions to the polarizing 

 plate, the ratio of the effects was totally changed, and was, in 

 general, reduced nearly to unity. This took place whether the 

 rhomb or the polarizing plate was moveable. The following ex- 

 periments will illustrate these statements : 



Polarizing and Analyzing Plates I and M ; Rhomb B ; Heat 

 from brass about 700°. Plane of total reflection perpen- 

 dicular to plane of primitive polarization. 



February 2. 1836. 



Mean. Ratio.* 



Plates parallel 



crossed . 

 parallel 



parallel . . 12.25 \ 



crossed . . 6.05 I 1185 51 : ™0 



parallel . 11.45 ' 



Other things as before. Plane of reflection inclined 45° to 

 plane of primitive polarization. 



February 2. 1836. 

 Plates parallel 

 crossed 



9°.25 ) 

 7.9 J 



85 : 100 



parallel 

 crossed 



9.85 ) 



8.4 j 



85 : 100 



43. When the plates 



I and K were used, 



the ratio was raised 



* Only 50 per cent, of the heat was polarized instead of 63, as in the Table (art 22). 

 The reason is, that the mica bundle M, used on this occasion, polarized less com- 

 pletely than that marked K. I have invariably found the per-centage of heat po- 

 larized after total reflection within rock-salt, in, or perpendicular to, the plane of pri- 

 mitive polarization, to agree most closely with the results obtained when no reflec- 

 tion had taken place. 



3 o 2 



