Radiation of Heat by Gaseous Matter. 287 



as before, that up to an absorption of 1 the effect is proportional 

 to the quantity of gas present, the absorption of each of the ele- 

 mentary gases, at a tension of 0*1 of an inch, would be about 

 0*0033; hence the absorption of boracic ether of O'l of an inch 

 tension is to that of air at the same tension as 



620 : 0-0033, 



which would give to the ether an energy 186,000 times that of air. 



I have already spoken of the blackness of ammonia at 30 inches 

 tension. Referring to Table I., its absorption is found to be 

 1195. In the last Table the vapour of acetic ether, possessing 

 only one-thirtieth of the tension of the ammonia, produces appa- 

 rently the same effect; its absorption is also 1195. Such facts 

 give one entirely new ideas of the capabilities of matter ; and 

 our wonder will not be diminished by the results to be recorded 

 further on. 



With both gases and vapours we find that it does not follow 

 that a gas which produces a larger effect than another at one 

 tension should surpass that other at all tensions. Some gases 

 start from a lower level than others, but finally attain an equal, 

 or even a greater elevation. If their absorptions were represented 

 by curves plotted from the same datum-line, these curves would 

 in some cases approach, and in some cases cross each other. At 

 a tension of 1 inch, for example, carbonic acid has more than 

 double the absorptive power of carbonic oxide, whereas at a ten- 

 sion of 30 inches they are equal ; indeed some of my experi- 

 ments show carbonic oxide to have the advantage. On the 

 22nd of October, for example, I found the deflection produced 

 by 2 inches of carbonic oxide to be 15°, while that of 2 inches of 

 carbonic acid was 38°. The two gases at a tension of 30 inches 

 gave these results : — 



o 



' Carbonic oxide 52 



Carbonic acid 51*5 



And again, on the 4th of November I obtained the following 

 relative effects : — 



Tensions. 



i ; ^ 



1*2 inch. 24 inches, 

 o o 



Carbonic oxide 12 57 



Carbonic acid 37 54 



The same remarks apply to vapours. Methylic alcohol, for 

 example, starts at a lower level than the iodide of ethyle, but 

 ascends more quickly, and finally reaches a much higher eleva- 

 tion. The same observation may be made of chloroform in 

 comparison with benzole aod the iodide of ethyle. 



[To be continued.] 



