212 Mr. E. H. Griffiths. [Jan. 17, 



11. "The Latent Heat of Evaporation of Water." By E. H. 

 GRIFFITHS, M.A., Sidney Sussex College, Cambridge. 

 Communicated by R. T. GLAZEBROOK, F.R.S. Received 

 December 28, 1894. 



(Abstract.) 



Section I. 



Although, the enquiry described in the paper,* of which this com- 

 munication is an abstract, has engaged my attention for the last two 

 years, the actual experiments on which the conclusions are based were 

 not performed until the months of September and October, 1894. 

 Many difficulties in the construction of the apparatus had to be over- 

 come, also the necessary standardisation of the instruments occupied 

 my leisure time for some months."!" 



The apparatus was designed so as to enable me to perform experi- 

 ments at temperatures from 10 to 60 C., and I hoped to carry out 

 my investigations over that range. Owing, howerer, to incidents 

 described in Paper L, I have been able to complete the enquiry at 

 two temperatures only, although a number of less satisfactory experi- 

 ments, performed in a different manner from that finally adopted, 

 give approximate determinations at other temperatures. 



The apparatus is, I regret to say, of a very complicated nature, 

 owing, in a great measure, to my desire to avoid observational errors 

 by as far as possible so arranging the machinery as to make it self- 

 recording and self -regulating. 1 do not, therefore, feel it possible to 

 convey any clear idea of it in this abstract, and will confine myself to 

 a short description of the method, and the communication of the con- 

 clusions to which the experiments have led me. 



The calorimeter was suspended by glass tubes in a chamber, the 

 walls of which were maintained at a constant temperature (0 )- The 

 methods by which was kept constant have been fully described in 

 a previous paper, J Since the publication of that communication 

 some additions have been made by which the apparatus has been so 

 improved that it maybe regarded as almost perfect in its action over 

 the range 10 to 60. 



A silver flask which contained the water to be evaporated was 

 placed within the calorimeter, and the whole of the calorimeter exterior 

 to the flask was filled originally with aniline, and afterwards with a 



* Referred to in this abstract as " Paper L." 



f Throughout this enquiry I have been assisted by Mr. C. Green, Scholar of 

 Sidney Sussex College, Cambridge, to whom I return my sincere tha,nks. 



J " The Mechanical Equivalent." ' Phil. Trans.,' 184 (1893), A, pp. 361504. 





