Radiation of Heat by Gaseous Matter. 



339 



tions of the gas from the tube was so much work done by the 

 residue. That residue became consequently chilled; into it the 

 face of the pile adjacent poured its heat, and a swing of the needle 

 on the negative side of 0° was the consequence. The limit of the 

 excursion was 20°. 



Olefiant gas, operated on in the same manner, produced on 

 entering the tube a swing of 67°, showing radiation ; and on 

 pumping out, a swing of 41°, showing absorption. After the 

 pumping out of the gas, and without introducing a fresh quan- 

 tity, dry air was again admitted -, the swing produced by the 

 dynamic radiation of the residue of the gas (0'2 of an inch in 

 tension) was 59°. On pumping out very quickly, the dynamic 

 absorption produced a deflection of nearly 40°. 



A little of the vapour of sulphuric ether was admitted into the 

 tube ; on the admission of dry air afterwards, the needle swung 

 from 0° to 61°; on pumping out, the needle ran up to 40° on the 

 opposite side. 



These and other experiments, which I confess gratified me 

 exceedingly, showed that, without resorting to any source of 

 heat external to the gaseous body itself, its radiation and ab- 

 sorption might be determined with extreme accuracy, and the 

 reciprocity of both phenomena rendered strikingly clear. In 

 fact, at this very time I had been devising an elaborate appa- 

 ratus for the purpose of examining the radiation of gases and 

 vapours, with a view to comparing it with their absorption ; but 

 no such apparatus would have given me results equal in accu- 

 racy to those placed within reach by the discovery of dynamic 

 radiation and absorption. 



The following Table is the record of a series of experiments in 

 connexion with this subject. The vapour in each case was ad- 

 mitted till the mercury column fell half an inch, and dry air was 

 admitted afterwards. 



Table IV. — Dynamic Radiation and Absorption of Vapours. 



Deflections. 



Bisulphide of carbon 

 Iodide of methyle 

 Benzole . 

 Iodide of ethyle 

 Methylic alcohol 

 Chloride of amylc 

 Amylene 

 Alcohol . . . 

 Sulphuric ether 

 Formic ether 

 Acetic ether 



Radiation . 



o 



14 



19-5 



30 



34 



36 



41 



48 



50 



64 



68-5 



70 



Absorptio; 



o 



6 



8 

 14 

 15-5 



23 



275 



34 

 38 

 43 



