Mathematics and General Phi/Hies. 375 



to the conclusions of M. Poisson respecting the variation of den- 

 sity of the fluid near the surface in capillary phenomena, and the 

 atomic constitution of bodies generally. With reference to the 

 latter part of the subject, Professor Hamilton stated, that the ato- 

 mic discontinuity, considered by M. Poisson as necessary in order 

 to the physical explanation, did not appear to him mathematically 

 requisite to the investigation of these laws. 



Mr Sang made some remarks on the effect of changes on tlie 

 surfaces of bodies, in illustration of the principles adverted to. 



M. Arago spoke on the theories of Laplace and Poisson on mo- 

 lecular action, and observed that the conclusion of M. Poisson, re- 

 presenting the change of density near the surface of fluids, could 

 be put to an experimental test by the observation of the angle of 

 complete polarization at these surfaces. 



Professor Powell then read a paper on the repulsion produced 

 by heat, as established by the contraction of Newton's rings, when 

 heat was applied to the glasses. 



Professor Stevelly mentioned some familial- facts of a different 

 kind, in confirmation of the result obtained by Professor Powell. 

 Mr Sang also made some remarks on the same subject, and Pro- 

 fessor Forbes stated the result of his repetition of the experiment 

 of Professor Powell, and alluded to the explanation given by him-^ 

 self of the vibrations of heated metals in connexion with the same 

 subject. 



Mr Addams described certain phenomena of mobility in the parti- 

 cles of precipitated silica when heated, which he seemed to think 

 were due to the same repulsive force. 



Mr Whewell read a letter from Mr Hailstone, accompanying a 

 table of barometrical observations, taken at short intervals. 

 - Professor Forbes remarked, that the momentary oscillations of 

 the barometer, adverted to by the author, had been already noticed 

 by other observers, and made some observations on the atmosphe- 

 ric waves, whose existence was doubted by the author. 



Professor Forbes read a short communication from Mr Christie, 

 on a remarkable meteorological phenomenon observed by him at 

 Woolwich. 



Mr Baily mentioned a similar phenomenon observed by him, and 

 described by ^Ir Faraday ; and Mr Whewell and Professor Powell 

 noticed the fact of the observation of the same phenomenon by 

 other observers. 



