Radiant Heat, and its Conversion thereby into Sound. 



495 



§ 7. Thermal Continuity of Liquids and Vapours. 

 I have amply illustrated by experiments, recently made, 

 the correspondence which subsists between A^apour absorption 

 and liquid absorption, when the quantities of matter traversed 

 in the two cases by the calorific rays are proportional to each 

 other. This correspondence, as I have already stated, was 

 established eighteen years ago. And though the result goes 

 to the very core of the discussion which my researches have 

 aroused, though in relation to that discussion they had, in my 

 estimation, a weight and import greater than those of any 

 other experiments published by me, they seem never for a 

 moment to have attracted the attention of those who have 

 taken part in the discussion. Here is the result, published 

 in 1864, which illustrates the point now under consideration : — 



Bisulphide of carbo 

 Chloroform 

 Iodide of methyl 

 Iodide of ethyl 

 Benzol . . . 

 Amylene . . 

 Sulphuric ether 

 Acetic ether . 

 Formic ether . 

 Alcohol . . . 





Absorption 



per 100. 





Vapour. 



Liquid 



0-48 



4-3 



8-4 



0-36 



6-6 



25-0 



0-46 



10-2 



46-5 



0-36 



15-0 



50-7 



0-32 



16-8 



55-7 



0-26 



19-0 



65-2 



0-28 



21-5 



73-5 



0-29 



22-2 



74-0 



0-36 



22-5 



76-3 



0-50 



22-7 



78-6 



The magnitude of the absorption in the liquids is far greater 

 than in the vapours, because the quantity of absorbent matter 

 is far greater in the former than in the latter ; but the order 

 of absorption is the same. 



When the vapours are doubled in quantity, the absorptions 

 are considerably increased. When trebled they are still further 

 augmented ; in other words, they approach more and more 

 in magnitude to the absorptions of the liquids ; but the har- 

 mony as regards order is never disturbed. What, then, would 

 occur if the vapours were so increased as to render the quan- 

 tities of matter in the two states, not proportional, but equal 

 to one another ? This is the question with which I now propose 

 to deal. At the time when the results above recorded were 

 obtained, I thought it probable that if a circular liquid layer 

 of a given diameter could be vaporized in a tube of the same 

 diameter, the absorption would remain unchanged. In other 

 words, I thought that the liberation of the molecules from 

 liquid cohesion would neither augment nor diminish their 



