178 



Messrs. J. B. Hannay and J. Hogarth. [Feb. 26, 



that, from experiments made with this tube with Mr. De La Rue's 

 chloride of silver battery on a former occasion, and quite independently 

 of the present question, it was estimated that a current having an 

 electromotive force of 400 volts was necessary to effect a discharge. 



Other tubes were tried, and were illuminated in the same way. 



When the tube was placed in the magnetic field, the discharge 

 underwent the modifications described by Pliicker, by Hittorf, and by 

 others. But it may be mentioned as a result of the extraordinary 

 strength of the field here employed that, whenever the tube was so 

 placed that the direction of discharge made any considerable angle 

 with the lines of magnetic force passing through it, the discharge was 

 completely extinguished. When the tube was removed to a weaker 

 part of the field, the discharge reappeared distorted in form, and 

 altered in colour, in a manner known to those who have experimented 

 in this direction. 



February 26, 1880. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. " On the Solubility of Solids in Gases." By J. B. Hannay, 

 F.R.S.E., F.C.S., and James Hogarth, F.C.S. Communi- 

 cated by Professor G. G. Stokes, D.C.L., LL.D., Sec. R.S. 

 Received February 14, 1880. 



The research which we now have the honour of submitting to the 

 Royal Society, and of which a preliminary notice was published in the 

 Society's Proceedings,* was instituted with the view of throwing 

 some further light upon what Dr. Andrews calls the " critical state " 

 of matter. In his famous Bakerian lecture, after a very careful dis- 

 cussion of the question, Dr. Andrews says :f " Carbonic acid at 35'5° C, 

 and under a pressure of 108 atmospheres, stands nearly midway 

 between the gas and the liquid, and we have no valid grounds for 

 assigning it to the one form of matter any more than to the other." 



* " Proc. Roy. Soc," vol. xxix, p. 324. 

 f "Phil. Trans.," 1869, p. 588. 



