and Polarization of Heat. 



161 



riments, of which the following is a brief summary, seem to in- 

 dicate. The coincidence has generally been more perfect, as the 

 steadiness of the source of heat admitted of more accurate com- 

 parison. The indications in the same line are alone intended to 

 be compared, as they are expressed in degrees of the multiplier, 

 the absolute amount of which would vary in different experi- 

 ments. The interposed film of mica No. 1 ., is that mentioned in 

 (54), as giving a red of the second order when placed between 

 the polarizing and analyzing plates crossed ; the film No. 2. gave 

 a plum-red of the first order under the same circumstances. 



Source of Heat. 



Mica 

 Plate. 



Increase of Intensity of Extra- 

 ordinary Pencil, by the De- 

 polarizing Action of the In- 

 terposed Crystal. 

 E 2 



Decrease of Intensity of Ordi- 

 nary Pencil, by the Depolariz- 

 ing Action of the Interposed 

 Crystal. 



F 2 _0 2 







Number of 

 Compari- 

 sons. 



Degrees of 

 Multiplier. 



Number of 

 Compari- 

 sons. 



Degrees of 

 Multiplier. 



Mercury below 500°, 



No. 2 



5 



0°23 



6 



0.26 



Brass about 700°, < 



No. 1 

 No. 1 

 No. 1 

 No. 1 

 No. 2 

 No. 2 



4 

 4 

 4 

 4 

 4 

 7 



0.46 

 0.35 

 0.51 

 0.59 

 0.44 

 0.75 



4 



4 

 5 



5 



7 



0.32 

 0.55 

 0.52 

 0.78 

 0.40 

 0.70 



Mean 



("27 

 (^ comp. 



0.517 



T29 

 "^ comp. 



0.545 



Incandescent Platinum, < 



No. 1 

 No. 1 

 No. 1 



No. 2 



3 

 4 

 4 

 6 



2.12 

 2.22 

 2.01 

 2.38 



3 

 4 

 5 

 6 



2.14 

 2.52 

 2.13 

 2.50 



Mean 



f 17 

 ( comp. 



2.18 



{18 



I comp. 



2.32 



Argand Lamp (with ' 



' No. 1 

 ( No. 2 



4 

 4 



0.97 

 1.90 



4 

 4 



1.00 

 1.74 



' Mean 



1 8 

 ( comp. 



1.43 



J 8 



( comp. 



1.37 



VOL. XIII. PART I. 



