1889.] Mr. J. Joly. On the Steam Calorimeter. 



45 



V. " On the Steam Calorimeter." By J. Joly, M. A. Commu- 

 nicated by G. F. Fitzgerald, F.R.S., F.T.C.D. Received 

 November 26, 1889. 



(Abstract.) 



The theory of the method of condensation has been previously 

 given by the author in the 'Proceedings of the Royal Society,' vol. 41, 

 p. 352. 



Since the publication of that paper a much more extended know- 

 ledge of the capabilities of the method has been acquired, which has led 

 to the construction of new forms of the apparatus, simple in construc- 

 tion and easily applied. Two of these are described and illustrated, 

 one of which is new in principle, being a differential form of the 

 calorimeter. The accuracy of observation attained by this latter form 

 is so considerable that it has been found possible to estimate directly 

 the specific heats of the gases at constant volume to a close degree of 

 accuracy. 



An error incidental to the use of the method arising from the 

 radiation of the substance, when surrounded by steam, to the walls of 

 the calorimeter, is inquired into. It is shown that this affects the 

 accuracy of the result to a very small degree, and is capable of easy 

 estimation and elimination. 



Further confirmation of the truth of the method is afforded in a 

 comparison of experiments made in different forms of the steam 

 calorimeter. 



Various tables of constants are given to facilitate the use of the 

 method, and the results of experiments on the density of saturated 

 steam at atmospheric pressures, made directly in the calorimeter, are 

 included. These are concordant with the deductions of Zeuner, 

 based on Regnault's observations on the properties of steam, and 

 were undertaken in the hope of affording reliable data on which to 

 calculate the displacement effect on the apparent weight of the sub- 

 stance transferred from air to steam. 



The communication is intended to provide a full account of the 

 mode of application of the steam calorimeter. 



VI. " On the Extension and Flexure of Cylindrical and Spherical 

 Thin Elastic Shells." By A. B. Basset, M.A., F.R.S. Re- 

 ceived December 9, 1889. 



(Abstract.) 



The usual theory of thin elastic shells is based upon the hypothesis 

 that the three stresses R, S, T, may be treated as zero, where R is the 



