ISO SECTION PHYSICS. 



down anhydrous salt, and if it is touched with the cryohydratc it 

 solidifies into cryohydrate. 



The PRESIDENT : We must return our best thanks to Professor 

 Clerk-Maxwell for his very curious communication illustrating the 

 unexpected condition in which matter may be found and its unexpected 

 tendency to change in various ways. To myself it has been par- 

 ticularly interesting to see how all these conditions of matter and their 

 tendency may be represented by a model of some tolerable simplicity 

 and how the geometrical properties of that model are capable of 

 illustrating and expressing the laws of these peculiar conditions of 

 matter. 



I believe Dr. Andrews, who has paid great attention to the molecular 

 condition of matter, is present, and we shall be glad to hear any com- 

 munication which he has to make. 



ON THE LIQUID AND GASEOUS STATES OF BODIES. 



Professor ANDREWS, M.D., F.R.S. : It is with some difficulty, not 

 being accustomed to address meetings of this kind, that I attempt to 

 speak on the subject of which I have given notice, more particularly as 

 it is a very wide subject and represents the work of nearly ten years. 

 The facts are so numerous that I am afraid in attempting to give even 

 a sketch of the entire subject I may end in being partially unintelli- 

 gible. At the commencement I wish to say that researches of this 

 kind are not researches on conditions of matter which cannot be 

 realized in Nature. It is highly probable that in the stellar regions, 

 and also in many of the larger planets of our own system, all the 

 conditions of matter to which I shall refer may actually exist. 

 Certain it is that we could produce them without any artificial means, 

 if it were possible to descend to the depths of our existing ocean, 

 and there to establish at certain intervals experimental laboratories. 

 Many years ago, as some of you will remember, Professor Leslie, of 

 Edinburgh, imagined that at the bottom of the ocean there was a 

 layer of condensed air heavier than water, and that there might be 

 inhabitants in that condensed atmosphere. Certain it is we can 

 reduce the gases to very nearly the same density as water to a 

 density at which, as I have seen myself, they barely rise in that 



