320 



Mr. J. B. Hannay. 



destroyed by the action of the gaseous molecules, so another series 



was tried at a lower pressure. Forty-two experiments were done : 



Mean temperature corrected 282°'50. 



Probable error o, 12. 



Mean pressure corrected 83 "18 atmos. 



Probable error 0'33 



Here we see that a large increase of pressure has not altered the 

 critical temperature at all, as was before seen to be the case with 

 alcohol. A series of capillary measurements was commenced with this 

 liquid, but a series of accidents interfered with the work, and only 

 twelve reliable readings were obtained, and no time has been at my 

 disposal since to finish the work ; but sufficient evidence of the course 

 of capillary action has already been gained from the other liquids to 

 draw conclusions as to the liquid state and its limit. 



Fig. 4. 



Three curves have been drawn to show the depression of the critical 

 temperature with increase of pressure, and these lines have been con- 

 tinued down the curve of vapour pressure to show the break at the 

 critical point. This will be clearly shown in curves Nos. XVII, XVIII, 

 and XIX, fig. 4. The consideration of these results yields a novel 

 mode of looking at the states of .matter which I have illustrated in 

 fig. 5. From this it appears we might classify matter under four states; 

 first, the gaseous which exists from the highest temperatures down to 

 an isothermal passing through the critical point and depending 

 entirely upon temperature or molecular velocity ; second, the vaporous, 

 bounded upon the upper side by the gaseous state and on the lower 

 by absolute zero, and depending entirely upon the length of the 

 mean free path, because shortening of the mean free path alters the 

 state ; third, the liquid bounded upon the upper side by the gaseous 

 state, and on the lower by the solid or absolute zero ; fourth, the solid 



