226 



KNOBLAUCH ON RADIANT HEAT. 



These numbers likewise remain unaltered when the adiatherma- 

 nous bodies above mentioned are heated by the metallic cylinder at 

 212° instead of the Argand lamp, although according to the 

 former experiments (pp. 204, 205, 206) the rays from these two 

 sources of heat are essentially different from one another. 



The subjoined table (the numbers in which, as in the former, 

 are each the arithmetic means of two observations) will prove 

 this beyond a doubt : — 



Table XVI. 



Thick- 

 ness in 

 milli- 

 metres. 



Substances inserted. 



Deflec- 

 tion by 

 direct 

 radia- 

 tion. 



Deflection produced after the insertion by the following 

 bodies heated for radiation by the hot metallic cylinder. 



Metal. Wood 



Porce- 

 lain. 



Paste- 

 board. 



1-5 

 1-4 

 1-4 

 4-4 

 3-7 

 1-4 



Red glass 



Blue glass 



Alum 



Rock salt 



Calcareous spar. . 

 Sulphate of lime 



35° 



35° 



10-25 

 9-17 

 4-00 



20-66 

 7-17 

 8-66 



10-00 

 9-25 

 3-92 



2066 



7-08 

 8-83 



10-25 

 917 

 4-00 



20-66 

 7-17 

 883 



1017 

 9-17 

 3-83 



20-75 

 7-17 

 8-66 



milli- 

 metres. 



15 

 1-4 

 14 

 44 



3-7 

 1-4 



Substances 

 inserted 



Red glass 



Blue glass 



Alum 



Rock salt 



Calcareous spar 

 Sulphate of lime 



Deflec- 

 tion by 

 direct 

 radia- 

 tion. 



35° 



35° 



Deflection produced after the insertion by the following 

 bodies heated for radiation by the hot metallic cylinder. 



Lamp- 

 black on 

 the side 

 next the 

 source of 

 heat, black 

 paper on 

 that next 

 the pile, or 

 vice vei'sd. 



10-25 

 9-17 

 3!)2 



20-66 

 7-08 

 8 83 



Lamp- 

 black on 

 the side 

 next the 

 source of 

 heat, ear- 

 that next 

 the pile, or 

 vice versd. 



10 17 

 9-25 



■1 00 



20 58 



7-25 



866 



Deflec- 

 tion after 

 insertion 



pro- 

 duced by 

 the rays 



of the 

 metallic 

 cylinder. 



10-16 

 9-18 

 3-95 



20 66 

 7-20 

 8-75 



