iOO 



Prof. TyndalPs Contributions to Molecular Physics. 



Four months subsequent to the performance of the above ex- 

 periments, a second series were made with olefiant gas, and the 

 following results obtained : — 



Table XXXIII. — Radiation through dry Olefiant Gas. Source, 

 small carbonic-oxide flame. 

 Tension in inches. Deflection. Absorption. From Table XXXI. 



1-0 



o 



11-4 



23-2 



48-0 



2-0 



170 



34-7 



55-5 



30 



21-6 



44-0 



60-3 



40 



24-8 



50-6 



65-1 



5-0 



27-0 



551 



68-6 



10-0 



32-1 



65-5 



74-3 



Beside the absorption by olefiant gas, I have placed that by 

 carbonic acid derived from Table XXXI. The superior power 

 of the acid is most decided in the smaller tensions ; at a tension 

 of an inch it is twice that of the olefiant gas. The substances 

 approach each other more closely as the quantity of gas aug- 

 ments. Here, in fact, both of them approach perfect opacity ; 

 and as they draw near to this common limit, their absorptions, 

 as a matter of course, approximate. 



The temperature of a hydrogen -flame, as calculated by Bun- 

 sen, is 3259° C, while that of a carbonic-oxide flame is 3042° C. 

 The foregoing experiments demonstrate that accord subsists 

 between the oscillating periods of these sources and the periods 

 of aqueous vapour and carbonic acid at a temperature of 15° C. 

 The heat of the flame goes to augment the amplitude, and not 

 to quicken the vibration. 



Sent through carbonic oxide, the radiation from the carbonic- 

 oxide flame gave the following absorptions : — 



Table XXXIV. — Radiation through Carbonic Oxide. Source, 

 carbonic-oxide flame. 



Tension in 



inches. 



Deflection. 



Absorption, 



1 





18'0 



29-0 



2 





27-0 



43-5 



4 





34-0 



56-4 



10 





37-3 



65-5 



The absorptive energy is here high— greater, indeed, than 

 that of olefiant gas ; it falls considerably short, however, of that 

 exhibited by carbonic acid. This result shows us that the main 

 radiant in the flame is its product of combustion, and not the 

 carbonic oxide heated prior to combustion. 



