368 



Professor W. Hamsay 



[May 8, 



is termed the " vapour- pressure " of water. If now the temperature 

 were raised to 110° we should have a greater initial volume for the 

 water-gas. It is compressible, by rise of the mercury, as before, the 

 relation of pressure to volume being, as before, represented on the 



diagram as an approximate hyperbola ; and, as before, condensation 

 occurs when volume is sufficiently reduced ; but this time at a higher 

 pressure. We have again a horizontal portion, rej)resenting the 

 pressure of water-gas at 110^ in contact with liquid water; again a 



