KADI ANT HEAT, AND ITS CONVERSION THEREBY INTO SOUND. 329 
The needle being brought accurately to zero by the compensating cube when the 
cell was empty, liquid sulphuric ether was poured in. The consequent deflection was 
42° 
Here vapour absorption and liquid absorption were so nearly alike as to stimulate me 
to further efforts. The entry in my note book on the 22nd ends with the remark : 
“ I purpose repeating this experiment on Monday, with the view of rendering the 
result secure.” 
On Monday, accordingly, the experiments were resumed, but they proved by no 
means so easy as I had hoped to find them. For five days I worked at the subject 
without coming to any satisfactory conclusion. The source, the mirror, the cell, the 
experimental tube, and the thermopile, were all in turn objects of scrutiny; but 
there still remained a difference between the action of the liquid and that of its 
vapour sufficient to throw doubt on the assertion of their identity. 
Fig. 5. ' 
o 
s 
At the conclusion of many trials and precautions I found the absorption of the 
vapour still distinctly in excess of that of the liquid. I had reduced the spherical 
aberration to a minimum, by confining the reflection to a small central area of the 
silvered mirror. Still the image of the incandescent lime, formed at the end T / of 
the experimental tube, was large enough to encroach a little on the annular space sur¬ 
rounding the aperture closed by the plate of rocksalt. Diaphragms of polished metal 
had also been used to lessen the amount of heat falling upon the pile. I figured to 
MDcecLxxxn. 2 tr 
