

ON LIQUID AND GASEOUS STATES. 153 



tions through plate glass. Accordingly this arrangement has been 

 made which I described the other day. I should mention that some 

 of these instruments are in the hands of different Professors, amongst 

 others of Professor Rijke of Leyden. I have sometimes found diffi- 

 culty in operating at the temperature of 100 from the tendency of the 

 tube to become greasy, and drops of water collecting upon it. This 

 for a long time gave me a great deal of trouble, but at last I found a 

 remedy, which was to pour boiling water over the tube, an operation 

 which even under a pressure of 300 atmospheres is unattended by any 

 danger provided the apparatus be at exactly the same heat as the 

 steam namely, 100 C. I should have further mentioned that in 

 order to make experiments above 100, you must bend the tube, and 

 introduce the end of it into a suitable medium, such as sulphuric acid 

 or melted spermaceti, or heated air ; the only limit to the temperature 

 being the softening of the glass. In all these cases so perfect is the 

 apparatus as regards pressure that all our difficulty is with the tem- 

 perature. I should mention another matter of importance. If you 

 run up the apparatus suddenly to a pressure of 200 atmospheres or 

 more, it will appear to leak ; this is caused by the compression of the 

 leathers. It requires some little time, in short, before everything be- 

 comes steady. Therefore, in some experiments, it is desirable to run 

 up the pressure a little above what you want for a few minutes, and 

 then bring it down to the proper point. 



Now, having given a general account of the apparatus, I will very 

 briefly refer to the results, and in order to make the subject as intel- 

 ligible as possible, I shall refer for a moment to a series of effects 

 which I think establish pretty clearly the remarkable fact, that between 

 water or any other liquid for it is not confined to one liquid more 

 than to another between any body in the liquid state and the same 

 body in the gaseous or vaporous state, not only is continuity pos- 

 sible, but we have been able to establish it by experiment. This 

 continuity has not been extended to the solid state, nor do I believe 

 that the ordinary plastic condition of the solid is a passage between 

 the solid and the liquid condition. That such a passage may be 

 hereafter effected is possible ; but as far as I can see my way at 

 present, it is a question which will involve an apparatus capable 

 of bearing a pressure of many thousands of atmospheres. I may be 



