358 



Professor Forees'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. 



Parallel 

 Crossed 

 Parallel 

 Crossed 

 Parallel 



Parallel 

 Crossed 

 Parallel 

 Crossed 

 Parallel 



Parallel 

 Crossed 

 Parallel 

 Crossed 

 Parallel 



Dynamical Effect. 



15?6 — 



4.2 

 15.75™ 



4.4 

 15.95 — 



J 



Mean. 



15.67 



15.85 



Argand without Reflector : 16 Inches. 



10.4 ~ 



3.0 

 10.45- 



2.95 

 10.65- 



Incandescent Platinum 



11.9 



3.45 



12.95: 

 3.7 



12.8 



Dark Heat from Brass, warmed by 



Parallel .... 10.55 



Crossed .... 4.05 



Parallel . . . .10.6 ~ 



Crossed . . . .3.9 

 Parallel . . . .10.5 



10.42 

 10.55 



16 Inches. 



12.42 

 12.87 



Ratio. 



27 : 100 



28 : 100 



29 : 100 

 28 : 100 



28 : 100 



29 : 100 



Alcohol : 16 Inches. 



10.57 

 10.55 



38 : 100 

 37 : 100 



