408 



KNOBLAUCH ON RADIANT HEAT. 



Table XXXVI IT {continued). 



Thickness 

 in milli- 

 metres. 



Substances inserted. 



Deflection 

 by direct 

 radiation. 



Deflection after 



'It^ZT ^>T— c"-'-- 



1-5 

 1-4 

 1-4 

 4-4 

 37 

 1-4 



1-5 

 1-4 

 1-4 

 4-4 



3-7 

 1-4 



1-5 

 1-4 

 1-4 



4-4 



37 

 1-4 



Red glass 



Blue glass 



Alum 



Rock salt 



Calcareous spar 

 Gypsum 



Red glass 



Blue glass 



Alum 



Rock salt 



Calcareous spar 

 Gypsum 



20° 



"26° 



25° 



25° 



1042 

 917 



8-08 

 1813 

 10-63 



9-25 



Deflection after the insertion 



11-62 



9-87 

 600 



Red glass 



Blue glass 



Alum 



Rock salt 



Calcareous spar 

 Gypsum 



25° 

 30° 



20-87 

 1413 

 11-63 



Deflection after the insertion 



9-00 

 8-00 

 6-50 



22-25 

 9-63 



10-38 



It is thus again shown, that the changes undergone by heat 

 on diffuse reflexion are occasioned both by the nature of the 

 sources of heat and the jiroperties of the reflecting body. 



This is connected with the fact, that tine rays of heat reflected 

 bv different substances, change, in a certain respect, their rela- 

 tions to one another. 



Thus the heat of the Argand lamp, when reflected by carmine, 

 is transmitted through gypsum less perfectly in comparison with 

 that reflected by white velvet ; the rays of red-hot platinum re- 

 flected by these surfaces, however, penneate this plate in the 

 same manner ; and the heat of the flame of alcohol passes through 

 it after reflexion by carmine comparatively better than when re- 

 flected by white velvet. The same occurs, under similar circum- 

 stances, v\'ith white lead and white wool. The rays of heat of 

 the Argand lamp, when reflected by red taffeta and peroxide of 

 copper, are transmitted by a plate of alum in a different propor- 

 tion ; whilst those of platinum at a red heat, when reflected by 

 the same surfaces, are so in the same proportion. 



These examples are sufficient to illustrate the process in ques- 



