324 Dr. Ramsay. On the Critical State of Gases. [Apr. 22, 



substance is supposed to exist in a peculiar condition, and Dr. 

 Andrews purposely abstained from speculating on tlie nature of the 

 matter, whether it be liquid or gaseous, or in an intermediate condi- 

 tion, to which no name has been given. As my observations bear 

 directly on this point, it may be advisable first to describe the experi- 

 ments I have made, and then to draw the deductions which appear to 

 follow from them. 



A piece of barometer tubing, about 3 inches long, was sealed at one 

 end and drawn into a capillary tube at the other ; after being filled 

 with methyl formate, it was exhausted, and after two-thirds of the 

 ether had evaporated, was sealed. By this means all air was removed 

 from the tube, which contained merely the ether and its vapour. This 

 tube was placed in a hole, drilled in a large block of copper. The 

 accompanying wood-cut shows its cross section. The block was placed 



'Q.T 





A , 



3 r C 



A, Hole for barometer-tube. B and C, Holes for thermometers. 



in an inclined position, so as to slope the barometer tube to an angle of 

 about 30°. 



1. On applying heat the temperature of the copper gradually rose to 

 221° '5 (corr.) ; during the rise the meniscus of the liquid gradually 

 became less curved, and at the above-mentioned temperature dis- 

 appeared. On cooling to 218° a mist was seen at the point where the 

 meniscus had disappeared, and the meniscus shortly afterwards became 

 again visible. 



2. Two similar tubes were prepared, one containing less and the 

 other more of the same ether; the point at which the meniscus dis- 

 appeared in the former was 228°, and in the latter 215°. 



3. A piece of barometer tubing was bent into the shape — 



and heated. At 250° the liquid had so expanded as to fill the whole 

 tube, although the temperature of the portion outside the heater could 

 not have much exceeded 100°, for it could be freely handled. The 

 liquid appeared in violent motion, and on cooling, before a meniscus 

 was observed, the lower portion of the tube became filled with mist. 



