374 Professor W. Bamsay on Liquids and Gases. [May 8, 



must be equal to that of the figure A F H. Dr. Young and I have 

 tried this experimentally, that is, by measuring the calculated areas; 

 and we found them to be equal. This can be shown to you easily by 

 a simple device, namely, taking them out and weighing them. As 

 this diagram is an exact representation of the results of our experi- 

 ments with ether, the device can be put in practice. We can detach 

 these areas which are cut out in tin, and place one in each of this j^air 

 of scales, and they balance. The fact that a number of areas thus 

 measured gave the theoretical results, of itself furnishes a strong 

 support of the justice of the conclusions we drew as regards the forms 

 of these curves. 



To attempt to explain the reasons of this behaviour would take 

 more time than can be given to-night ; moreover, to tell the truth, we 

 do not know them. But we have at least partial knowledge ; and we 

 may hope that investigations at present being carried out by Professor 

 Tait may give us a clear idea of the nature of the matter, and of the 

 forces which act on it, and with which it acts, during the continuous 

 change from gas to liquid. 



[W. E.] 



