404 



KNOBLAUCH ON RADIANT HEAT. 



It is hence evident that e. g. the needle of the galvanometer, 

 which had been deflected 13° by the reflexion of the heat from 

 the above source, receded to ]0° on inserting the red glass 

 when the heat was reflected by carmine, and to 7° when by 

 black paper; or when it had deviated 20°, on the insertion of 



Table XXXV. 



Thickness 

 in milli' 

 metres. 



Substances inserted. 



Deflection 

 by direct 

 radiation. 



^rl^^lT «^-"- '^"""-- 



Deflection after 



]-5 



1-4 

 1-4 



4-4 

 3-7 



1-4 



Red glass 



Blue glass 



Alum 



Rock salt 



Calcareous spar 



Gypsum 



13° 



20° 



7-04 



6-00 

 3-66 



1813 

 10-63 



9-25 



7-71 



6-46 

 3-79 



1800 

 12-94 



5113 



8-79 



7-00 

 4-54 



18-50 

 14-81 



11-63 



It was found that the heat reflected in this instance by car- 

 mine, when it again produced a direct deflection of 13°, on in- 

 serting the red glass produced a deflection in the thermo-multi- 

 plier of 8°*79, and that reflected by black paper under the same 

 circumstances an indication of 6°'42 ; or on the insertion of the 

 calcareous spar, the former a deflection of 14°'81, the latter of 

 9°"69, when the direct action of the reflected heat had caused the 

 needle as before to deviate to 20°. 



Thus the differences in the heat reflected by carmine and 



Table XXXVI. 



Thus, when the heat of this flame was reflected by carmine, 

 so as to deflect the needle of the thermoscope to 13°, on inserting 



