of Heat by Gaseous and Liquid Matter. 91 





Table X, 



— Olefiant Gas. 





Length. 





Absorption per 



100. 



1st 



2nd 



1st 



2nd 



Both 



chamber. 



chamber. 



chamber, 



chamber. 



chambers, 



12-2 



372 



54-8 



70-0 



76-3 



15-4 



34-0 



59-1 



72-7 



771 



19-8 



29-6 



67-8 



70-4 



770 



23-8 



25-6 



69-2 



70-2 



776 



36-3 



13-1 



72-8 



60-3 



78-8 



The absorptions of both chambers in this Table are almost 

 exactly 10 per cent, higher than those found with the gas gene- 

 rated under Dr. Frankland's superintendence. 



A few remarks on these results may be introduced here. In 

 the case of carbonic oxide (Table VI.), we see that while a length 

 of 2*8 inches of gas is competent, when acting alone, to intercept 

 68 per cent, of the radiant heat, the cutting off of this length 

 from a tube 49*4 inches long, or, what is the same, the addition 

 of this length to a tube 46-6 inches long, makes no sensible 

 change in its absorption. The second chamber absorbs as much 

 as both. The same remark applies to carbonic acid, and it is 

 also true within the limits of error for nitrous oxide and olefiant 

 gas. Indeed it is only when 8 inches or more of the column 

 have been cut away that the difference begins to make itself felt. 

 Thus, in carbonic oxide, the absorption of a length of 41*4 being 

 12'2, that of a chamber 49*4, or 8 inches longer, is only 12*9, 

 making a difference of only 0*7 per cent., while the same 8 inches 

 acting singly on the gas produces an absorption of 9' 6 per cent. 

 So also with regard to carbonic acid; a tube 41*4 absorbing 

 12*7 per cent., a tube 49*4 absorbs only 13*0 per cent., making 

 a difference of only 0*3 per cent. As regards olefiant gas (Table 

 IX.), while a distance of 8 inches acting singly effects an absorp- 

 tion of 44 per cent., the addition of 8 inches to a tube already 

 41 # 4 inches in length raises the absorption only from 65*3 to 

 67*5, or 22 per cent. The reason is plain. In a length of 

 41 '4 the rays capable of being absorbed by the gas are so much 

 diminished, so few in fact remain to be attacked, that an addi- 

 tional 8 inches of gas produces a scarcely sensible effect. Simi- 

 lar considerations explain the fact that, while by augmenting the 

 length of the first chamber from 2'8 inches to 15*4 inches we 

 increase the absorption of olefiant gas nearly 20 per cent., the 

 shortening of the second chamber by precisely the same amount 

 effects a diminution of barely 4 per cent, of the absorption. All 

 these results conspire to prove the heterogeneous character of the 

 radiation from a source heated to about 250° C. 



The sum of the absorptions placed side by side with the 



