358 Professor Forses’s Researches on Heat. 
been led to the conclusion, that some kinds of heat are more po- 
larizable at a given incidence than others. Between heat from 
an Argand lamp, and that from platinum rendered incandescent 
by the flame of alcohol, there is little difference ; but heat, un- 
accompanied by light, is much less polarizable than luminous 
heat, and that apparently in proportion to the lowness of its tem- 
perature. I may take the opportunity of giving one or two ex- 
amples of such experiments. 
Mica Plates I and K. Argand Lamp, with Chimney and Reflec- 
tor : 16 Inches from Centre of Pile. 
Dynamical Effect. Mean. Ratio. 
Parallel ; : 4 : 15.6 Estes bs 
Crossed ‘ p : . 42 15.67 27 : 100 
Parallel é ; : walbees = 
Crossed ; é A - 44 ! 15.85 28 : 100 
Parallel : ; : ~ 15.95——~— 
Argand without Reflector : 16 Inches. 
Parallel ; : : - 10.4 ——- 
Crossed . : . J, 18.0, 10.42 29 : 100 
Parallel : . ‘ O45 
Crossed 5 5 : OO } 10.55 28 : 100 
Parallel : ; , SY Se 
Incandescent Platinum : 16 Inches. 
Parallel : 3 2 >» 1g 
Crossed , ; a . 8.45 12.42 28 : 100 
Parallel 4 : by Sl Obamas 
Crossed ; ‘ é 3.7 } 12.87 29 : 100 
Parallel : : 6 SICH ieee 
Dark Heat from Brass, warmed by Alcohol : 16 Inches. 
Parallel Q > t sat LO:5 
Crossed A 4 ’ » 4.05 ' 10.57 38 : 100 
Parallel i j ; OG es 
Crossed : . : OG ; 10.55 37 : 100 
Parallel : : : © LOS eerecers 
