RADIANT HEAT, AND ITS CONVERSION THEREBY INTO SOUND. 
327 
it incandescent, had to he very carefully prepared, freshly amalgamated zinc plates 
being used in each fresh battery. The requisite deflection of a tangent compass being 
produced, it was kept constant by means of a rheochord throughout the day. When 
the battery showed signs of rapid falling it was always renewed. It would be tedious 
to dwell upon the precautions taken to protect the source and the pile from the least 
agitation of the air. Such precautions are essential, but their necessity and form must 
be learnt by each experimenter for himself. 
§. 7. Thermal Continuity of Liquids and Vapours. 
I have amply illustrated by experiments, recently made, the correspondence which 
subsists between vapour 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 a result, published in 1864, which illustrates the 
point now under consideration:— 
Absorption per 100. 
Bisulphide of Carbon . . . 
0-4S 
Vapour. 
43 
Liquid. 
8-4 
Chloroform. 
0-36 
6-6 
25-0 
Iodide of Methyl. 
0-46 
10*2 
46-5 
Iodide of Ethyl. 
0-36 
15-0 
507 
Benzol. 
0-32 
16-8 
557 
Amylene. 
0-26 
19-0 
65-2 
Sulphuric Ether. 
0-28 
21-5 
73-5 
Acetic Ether. 
0-29 
22-2 
74-0 
Formic Ether. 
0*36 
22-5 
76-3 
Alcohol. 
050 
227 
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 harmony as 
regards order is never disturbed. What then would occur if the vapours were so 
increased as to render the quantities 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 
