Prof. TyndalFs Contributions to Molecular Physics. 451 



The differences here are inconsiderable,, and lean to neither side ; 

 within these limits, therefore, the calibration must be correct ; it 

 shall be tested more severely in another part of this paper. 



§ ]V. Absorption of the same heat by the same vapours when the 

 quantities of vapour are proportional to the quantities of liquid. 

 — Comparative view of the action of liquids and their vapours on 

 radiant heat. 



We are now in a condition to compare the action of a series 

 of volatile liquids with that of the vapours of those liquids upon 

 radiant heat. 



Commencing with the substance of the lowest absorptive 

 energy, and proceeding to the highest, we have the following 

 order of absorption : — 



Liquids. Vapours. 



Bisulphide of carbon. Bisulphide of carbon. 



Chloroform. Chloroform. 



Iodide of methyle. Iodide of methyle. 



Iodide of ethyle. Iodide of ethyle. 



Benzole. Benzole. 



Amylene. Amylene. 



Sulphuric ether. Alcohol. 



Acetic ether. Formic ether. 



Formic ether. Sulphuric ether. 



Alcohol. Acetic ether. 

 Water. 



Here, as far as amylene, the order of absorption is the same 

 for both liquids and vapours. But from amylene downwards, 

 though strong liquid absorption is in a general way paralleled 

 by strong vapour absorption, the order of both is not the same. 

 There is not the slightest doubt that next to water alcohol is the 

 most powerful absorber in the list of liquids ; but there is just 

 as little doubt that the position which it occupies in the list of 

 vapours is the correct one. This has been established by reite- 

 rated experiments. Acetic ether, on the other hand, though 

 certainly the most energetic absorber in the state of vapour, falls 

 behind both formic ether and alcohol in the liquid state. Still, 

 on the whole, I think it is impossible to contemplate these results 

 without arriving at the general conclusion that the act of absorp- 

 tion is in the main molecular, and that the molecule maintains its 

 power as an absorber and radiator when it changes its state of 

 aggregation. Should, however, any doubt linger as to the cor- 

 rectness of this conclusion, it will speedily disappear. 



