164 Professor Forses on the Refraction 
which, whilst it points out the mode of operating, will exhibit the 
constancy and considerable magnitude of these effects, amidst 
the complicated changes of condition to which the heat is sub- 
jected. The columns marked “corrected,” have a small correc- 
tion applied for the gradual alteration in the quantity of heat 
reaching the pile, which corrections are interpolated from the 
successive observations marked (1), (2), (3), &c. which are made 
under similar circumstances. 
1835. Jan. 16.—Source of Heat. Incandescent Platinum. Pola- 
rizing Mica Plates Eand F. Film of Mica interposed, No. 1. 
Position of |Principal Section Total Po- | Depolariza- |Total Po- iDiato is i 
Mica plates.| of interposed Multiplier. larization. tion. larization | 2102 Ratio. 
Mica, at Corrected. Corrected. 
[E at 0°] (45° (1) | 149.82 [isso + 2.8 
F at 90°|1 0 120 Sean 6.0 | 2.75 
Beat 20; e 18.0} —2.7 
45 15 3 bécebBess ees aie 
sias a) laatigh: OL SARE. 42.2 
OR {0 12 6) ive i] pea ilaand 
| f 0 16.6 me § 
Fat 0 45 14. MO seeqaaes’ 2 4 
SCARE (Opler cs $2.5 
F at 90 {5 11.6) 48 4.9 | 2.65 
Fata |J° 16 4) Ba es 8) 
é { ae 34} pene ! 
as Cay 815 eiey | la 42.0 
0 
Earl he 11.8) 45 | 22 
a = 0 oO 
F at 0 { 4h 13 's} Rospadasdeea A 
(45 () | 13.6 
F at 90 { 0 aha 2} \ 
0 16.1 j 
F at 0° 1s ig} [een 
F at 90° tN Ae 6} 
0 15 .6 
F at 0° 45 13. 5} scavetacabes 
When the analyzing plate F is said to be at 0°, it is parallel 
to the plate E. When the principal section of the interposed 
film is at 0°, it is parallel to the plane of incidence at the plate 
