222 G. HARKER. 



at the above experiment it appears likely, in confirmation 

 of what lias already been said, that the thermometer c was 

 showing a lower temperature than the temperature of the 

 entering vapour. This of course leaves a doubt as to 

 whether the vapour from the solution was not deriving 

 heat from the jacket, and whether if the experiment had 

 been continued, the temperature of the vapour would not 

 have risen higher than the solution itself, showing definitely 

 that the vapour was being superheated by the jacket. 



Seeing that the main point at issue is whether the tem- 

 perature of the vapour from a boiling solution is or is not 

 higher than the vapour from the boiling pure solvent, it 

 does not seem necessary to prove that the temperature 

 of the vapour is identically the same as that of the boiling 

 solution. If a substantial difference between the tem- 

 perature of the vapour arising from a boiling solution and 

 from the boiling pure solvent can be established, the main 

 purpose of the enquiry will be achieved. 



It is claimed that the experiments now to be described 

 establish this difference in a simple but direct manner. 

 They have been conducted with the view of eliminating 

 auy possibility of raising the temperature of the vapour by 

 heat from an outside source, and, while the observed tem- 

 perature of the vapour has been much below that of the 

 boiling solution, it has been substantially higher than 100°, 

 the temperature of the vapour from the boiling pure solvent 

 water. From the manner in which the experiments were 

 conducted, and owing to the care taken not to add heat, 

 loss of heat from the vapour after leaving the boiling solu- 

 tion was unavoidable, yet in spite of this loss the vapour 

 still showed a temperature much higher than 100°. 



The experiments were carried out in a hypsometer kindly 

 lent by Professor Pollock from the Department of Physics 

 of the University. As will be seen from the diagram (Fig. 



