406 



KNOBLAUCH ON RADIANT HEAT. 



or the needle receded ftie first time from 20° to 10°'75, the 

 second time from 20^ to 8°, when the plate of calcareous spar 

 was introduced between the reflecting surface and the thermal 

 pile. 



On comparing these results with the former, it is evident that 

 the differences which were found on the passage of the heat of 

 the flame of alcohol after reflexion by carmine and black paper 

 through red glass and calcareous spar, were less than those which 



Table XXXVII. 



Hence, in this instance, the heat reflected by carmine and 

 black paper was transmitted through red glass and calcareous 

 spar in exactly the same manner ; for when their direct action 

 produced a deviation of 13°, they both deflected the needle of 

 the galvanometer to 3°"25 when the red glass was inserted, or, 

 the direct deflection being 20°, to 5°*25-5°*05 when the plate 

 of calcareous spar was introduced between the reflecting surface 

 and the thermoscope. Nor were the rays, when reflected by 

 other surfaces, more distinguishable by any one of the diatherma- 

 nous substances, either from each other or from those unreflected. 



Thus with these sources of heat no differences could be de- 

 tected after diffuse reflexion. 



Table XXXVIII. 



