Second Series.— Polarization by Refraction. 359 
22. These are given as examples of the usual mode of pro- 
ceeding with such experiments, the zero point being ascertained 
between each observation, and the dynamical effect reckoned 
from it. On the whole, I obtained for the proportion of heat 
polarized, or stopped in the transverse position of the plates, the 
following numbers : 
Plates I and K. 
Source of Heat. Rays out of 100, polarized. 
Argand Lamp, ; : é “ : . : ; 72 to T4 
Incandescent Platinum, . : ; , : ; ; 72 
Brass heated to about ‘700°, . 3 : . 63 
Heat from the same source transmitted rome bas, , 72 
Mercury in a crucible at 410°, F ; t F : 48 
Boiling Water, : : : : , é 2 P 44 
Plates G and H. 
Argand Lamp, : ; / 4 : : - ; 82 
Incandescent Platinum, : ; ; : . ‘ 19 
Brass heated to about 700°, . : ’ 68 
Heat from the same source transmitted throat: ae 2 13 
Boiling Water, ! i 5 A 3 ' x é 49 
It thus appears that the Plates G and H are capable of polarizing 
no less than 82 per cent. of some kinds of incident heat: these 
plates I began to use in the commencement of December last. 
23. The unequally polarizable nature of different kinds of 
heat having been controverted, I took several methods of as- 
suring myself that the observed effects were not due to in- 
equalities in the dimensions of the sources of heat employed, or 
to their variable distances from the pile. A multitude of proofs 
might be given, but I will content myself with stating one or 
two of the most decisive. 1. Incandescent platinum and dark 
hot brass were successively placed at the same distance of twelve 
inches from the pile ; a thin plate of glass being placed between 
the latter and the pile, and two thick plates of glass between the 
VOL. XIII. PART II. 3N 
