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PROCEEDINGS OF SOCIETIES. 
Royal Microscopical Society. 
King’s College, June 6 , 1877 . 
The minutes of the preceding meeting were read and confirmed. 
A list of donations to the Society since the last meeting was read, 
and the thanks of the meeting were voted to the donors. 
A paper “ On the Thermo-dynamic Origin of the Brownian 
Motion,” by the Rev. Joseph Delsaulx, of Louvain, was read by the 
Secretary. (The paper will be found printed at p. 1.) 
A note from the President of the Society upon the subject of the 
paper, which had been submitted to him for perusal, was also read by 
the Secretary. 
The Chairman proposed a vote of thanks to the author of the 
paper : carried unanimously. 
Mr. W. N. Hartley said it would be remembered that on a former 
occasion he read a paper before the Society upon the fluid found in 
rock cavities, and since that time he had written a paper containing 
some further observations, and this paper had been read before the 
Royal Society by Professor Stokes. Before reading a short note 
which he had brought to the meeting, he wished just to refer to the 
contents of his paper to the Royal Society. In certain cavities of 
rock crystal he had found that the contained bubble was repelled 
when a hot wire was applied ; but in other cavities, under apparently 
the same circumstances, the bubbles were attracted. He gave an 
explanation of this at the time, which had since been improved upon 
by Professor Stokes. When a capillary tube had a small quantity of 
liquid introduced, the liquid would form a kind of plug, and when 
heat was applied to one end it was found that this liquid plug was 
repelled by heat ; and Professor Stokes informed him that this was 
caused by the diminution of the surface tension of the liquid. In 
the course of his observations on fluid contained in rock cavities, he 
had been led to the conclusion that the liquid in some of them was 
carbonic acid, and that at a temperature of 31° C. it existed there 
under a tension of 109 atmospheres, and in this case repulsion was 
caused by heat. Professor Stokes explained this by saying, that by 
heat a portion of the gas with which the liquid was saturated was 
driven off, and by this means the surface tension was increased, 
causing the bubble to move away. He made some further experi- 
ments, and found that an extremely slight increase of temperature 
caused a vibrating bubble to cleave to the heated side of the cavity, 
but, when the heat was equalized, the original movement continued. 
Vibrating bubbles of liquid carbonic acid he found could be of much 
larger size than those of water only. He also concluded that, as all 
bodies were always altering in temperature, it was impossible to 
maintain any body equally heated in every part ; and if it were 
correct that the movements of bubbles were due to the alteration of 
