Prof. Tyndall's Contributions to Molecular Physics. 449 



Table IX. — Radiation of heat through Vapours. Source, red- 

 hot platinum spiral. Tension, 0'5 of an inch. 



Name of vapour. Deflection. Absorption per 100. 



o Mean. 



Bisulphide of carbon . . 17'0 4*7 \ ^.» 



Bisulphide of carbon . . 16*8 4*6 J 



Chloroform 22-5 6-21 a .o 



Chloroform 22«8 63 J 



Iodide of methyle . . . 34-0 9-7 1 q . 7 



Iodide of methyle . . . 34'0 9'7 J 



Iodide of ethyle .... 46'0 18-0 \ -, -.« 



Iodide of ethyle .... 45-5 176 J 



Benzole 48-5 20 ' 4 \9fWt 



Benzole 48'5 20-4 J rfU "* 



Amylene 56*3 27*3 1 ^7.0 



Amylene 56'2 27'2 j Ai 



Total heat 78-3 1000 



The absence of all caprice or uncertainty in the measurements 

 is, I think, demonstrated by the foregoing Table, which is simply 

 an average sample of the degree of coincidence obtained in sepa- 

 rate measurements. Two determinations were made in each 

 case; and it will be seen that while, in some instances, the 

 second experiment yielded the same result as the first, in one 

 instance only does the difference amount to half a degree of the 

 galvanometer. 



The foregoing measurements were executed on the 5th of 

 October. On the 7th they were in part repeated, with the fol- 

 lowing results : — 



Table X. 

 Name of vapour. Deflection. Absorption. 



o 



Bisulphide of carbon ... 16*5 4*7 



Chloroform 22*8 6-5 



lode of methyle 330 9*6 



Iodide of ethyle 45'0 17*7 



Benzole 48-0 206 



Amylene 55'3 27*5 



Alcohol 55-7 28-1 



Formic ether 58'2 31-4 



Sulphuric ether 58'5 31-9 



Acetic ether 59*9 34-6 



Total heat 780 100*0 



Placing these results beside those recorded in Table IX., the 

 manner in which they check each other will appear. 



