Radiation of Heat by Gases and Vapours. 187 



of the scale, as far as my inquiries have hitherto proceeded. 

 The action of every other vapour is less than that of sulphuric 

 ether, and greater than that of bisulphide of carbon. 



A very singular phenomenon was repeatedly observed during 

 the experiments with bisulphide of carbon. After determining 

 the absorption of the vapour, the tube was exhausted as perfectly 

 as possible, the trace of vapour left behind being exceedingly 

 minute. Dry air was then admitted to cleanse the tube. On 

 again exhausting, after the first few strokes of the pump a jar was 

 felt and a kind of explosion heard, while dense volumes of blue 

 smoke immediately issued from the cylinders. The action was 

 confined to the latter, and never propagated backwards into the 

 experimental tube. 



It is only w.'ith bisulphide of carbon that this effect has been 

 observed. It may, I think, be explained in the following man- 

 ner : — To open the valve of the piston, the gas beneath it must 

 have a certain tension, and the compression necessary to produce 

 this appears sufficient to cause the combination of the consti- 

 tuents of the bisulphide of carbon with the oxygen of the air. 

 Such a combination certainly takes place, for the odour of sul- 

 phurous acid is unmistakeable amid the fumes. 



To test this idea I tried the effect of compression in the air- 

 syringe. A bit of tow or cotton wool moistened with bisulphide 

 of carbon, and placed in the syringe, emitted a bright flash 

 when the air was compressed. By blowing out the fumes with 

 a glass tube, this experiment may be repeated twenty times with 

 the same bit of cotton. 



It is not necessary even to let the moistened cotton remain in 

 the syringe. If the bit of tow or cotton be thrown into it, and 

 out again as quickly as it can be ejected, on compressing 

 the air the luminous flash is seen. Pure oxygen produces a 

 brighter flash than atmospheric air. These facts are in har- 

 mony with the above explanation. 



Table VII. — Amylene. 

 Unit-measure y^th of a cubic inch. 



Absorption. 



asures. 



<— 

 Observed. 



Calculated. 



1 



34 



4-3 



2 



8-4 



8-6 



3 



12-0 



129 



4 



16-5 



17-2 



5 



21-6 



21-5 



6 



26-5 



25-8 



7 



30-6 



301 



8 



35-3 



34-4 



9 



390 



387 



10 



44-0 

 02 



430 



