254 On Water and Steam. On Hindoo Astronomy. [Dec. 10, 



III. " On some of the Properties of Water and of Steam." By 

 WILLIAM RAMSAY, F.R.S., Professor of Chemistry in Uni- 

 versity College, London, and SYDNEY YOUNG, Professor of 

 Chemistry in University College, Bristol. Received Novem- 

 ber 5, 1891. 



(Abstract.) 



This investigation forms one of a series, former members of which 

 refer to the thermal properties of ethyl oxide and various alcohols. 

 Owing to the high temperature of the critical point of water, the 

 work was confined to comparatively low temperatures. Tables are 

 given in the paper of the orthobaric volumes of liquid water at tem- 

 peratures between 100 and 270; of the compressibility of water at 

 different temperatures ; of the vapour-pressures of water up to 270 ; 

 and of the density of the vapour of water under various conditions of 

 temperature and pressure. Regnault's measurements of vapour- 

 pressure do not extend beyond 220 ; and the results of this investi- 

 gation confirm them in a remarkable manner, besides amplifying 

 them. The densities of the saturated vapour, also, measured 

 directly, are nearly identical with those calculated from Regnault's 

 determinations of heats of vaporisation ; but near the condensing 

 point of steam, especially at low temperatures, the pressure is too 

 low, owing to the adhesion of water-vapour to glass, which causes 

 condensation at pressures below the vapour-pressures. This neces- 

 sarily renders the measurements near the condensing points uncertain, 

 but the numbers calculated from Regnault's results give volumes for 

 saturated steam agreeing sufficiently well with those obtained by 

 direct measurements at volumes somewhat larger than those of the 

 saturated vapour. It is probable that the real isochoric lines for 

 water show a linear relation between temperature and pressure ; but, 

 owing to the circumstance mentioned, they deviate from rectilinearity 

 near the condensing-points of the vapour. 



IV. " On Hindoo Astronomy." By W. BRENNAND. Communi- 

 cated by C. B. CLARKE, F.R.S. Received November 10, 

 1891. 



(Abstract.) 



Introduction. Gives a short history of Indian astronomy, as known 

 in Europe in the last century. 



Treats of Indian astronomical ceras, and gives some account of the 

 Siddhantas and their authors, &c. 



Ends with an investigation of the great number called the Kalpa, 

 of 4,320,000,000 years, showing its uses in astronomical calculations, 



