4 



Prof. J. Thomson on the 



[Nov. 16, 



line, when we regard the coordinate axes for pressures and volumes as 

 being horizontal and vertical respectively. Now in the diagram here sub- 

 mitted the continuous curves (that is to say, those which are not dotted) 



are obtained from Dr. Andrews's diagram, with the slight alteration of 

 substituting, in accordance with the explanations just given, an abrupt 

 meeting instead of the curved transition between the curve for the liquid 

 state and the upright line which shows the boiling stage. Looking to 

 either of the given curves which pass through boiling, and, for instance, 

 selecting the curve for 13°' 1, we perceive, from what has been said as to 

 the conditions to which boiling by bumping is due, that for the tempera- 

 ture pertaining to this curve the liquid state does not necessarily end at 

 the boiling pressure for this temperature, and that thus in the diagram 

 the curve showing volumes for the liquid state must not cease at the foot 

 of the upright line which marks the boiling stage of pressure, but must 

 extend continuously, for some distance at least, into lower pressures in some 

 such way as is shown by the dotted continuation from a to b. But now 

 the question arises, Does this curve necessarily end at any particular 

 point b ? We Know that the extent of this curve in the direction from a 

 towards or past b, along which the liquid volume will continue to be re- 



