402 



KNOBLAUCH OX RADIANT HEAT. 



Thus the rays of heat reflected by white velvet pass through 

 alum and gypsum in a greater, through calcareous spar in an 

 equal, and through red and blue glass and rock salt in a less 

 proportion than those reflected by carmine. The heat reflected 

 by peroxide of tin passes through red glass more freely, blue 

 glass, alum and rock salt in the same proportion, and calcareous 

 spar and gypsum in a less degree than that reflected by mother- 

 of-pearl. The values obtained on the transmission of the heat 

 reflected by black lac and black cloth through the above bodies 

 exhibit a similar variation. The rays reflected by red and green 

 velvet permeate red and blue glass, alum and rock salt in the 

 same, calcareous spar and gypsum in a different manner. 



It would be tedious to consider in detail the other instances, 

 which lead to similar results, and completely confirm the position 

 already advanced (p. 202), viz. that the transmission of heat 

 through diathermanous media depends solely upon the nature 



Table XXXIII. 



I. I first produced reflexion from those surfaces which in the 

 previous observations had exhibited the greatest differences. 

 The results to which the experiments with the Argand lamp led, 



Table XXXIV. 



Thicknesi 

 in milli- 

 metres. 



Substances inserted. 



Deflection 

 by direct 

 radiation. 



Deflection after 



Metalornot n _ o 



reflected. Gypsum. Carmme. 



1-5 



1-4 

 1-4 



4-4 

 3-7 



1-4 



Red glass 



Blue glass 

 Alum 



Rock salt 



Calcareous spar , 



Gypsum 



13° 



20° 



1-50 



650 

 5-00 



18-00 

 12-12 



9-87 



8-75 



6-75 

 6-25 



1800 

 15-50 



13-00 



1000 



700 

 7-25 



18-37 

 16-75 



13-87 



