248 



Mr. J. Joly. 



[Nov. 18, 



November 18, 1886. 



THE PRESIDENT in the Chair. 



In pursuance of the Statutes, notice of the ensuing Anniversary 

 Meeting was given from the Chair. 



The Right Hon. Lord Thurlow was admitted into the Society. 



Professor Bonney, Sir James Cockle, Mr. Preece, Dr. Rae, and 

 Mr. Stainton, having been nominated by the President, were by ballot 

 elected Auditors of the Treasurer's accounts on the part of the 

 Society. 



The Presents received were laid on the table, and thanks ordered! 

 for them. 



The following Papers were read : — 



I. " On the Method of Condensation in Calorimetry." By 

 J. Joly, B.E., Assistant to the Professor of Civil Engineer- 

 ing, Trinity College, Dublin. Communicated by Professor 

 Fitzgerald, F.R.S. Received June 28, 1886. 



(Abstract.)* 



A substance at the initial temperature of the atmosphere, 

 suddenly immersed in a saturated vapour at the higher temperature 

 t%°, abstracts from it a quantity of heat equal to WC(t 2 ° — ^°), where 

 C is the thermal capacity of the substance between the limits t£ 

 and t 2 °, and W its weight. There is then a weight w of the vapour 

 precipitated, so that 



WC(t 2 °-t 1 c )=w\, 

 \ being the latent heat of the vapour. 



By the observation of the weights and the temperatures, either c or 

 \ may be the unknowns sought from the equation. The method is, 

 in short, applicable to the determination of the specific heat of a 

 substance or the latent heat of a vapour. 



The paper contains an account of experiments illustrating the 

 application of this method of condensation to the determination of 

 the specific heats of substances. The condensation of steam is em- 

 ployed, its latent heat being accurately known, and its use affording 



* This paper is printed in full at p. 352. 



