622 report— 1884. 



equilibrium. All that I have said in favour of the model vortex gas composed of 

 perforated solids with fluid circulations through them holds without modification 

 for the purely hydrokinetic model, composed either of Helmholtz cored vortex 

 rings or of coreless vortices, and we are now troubled with no such difficulty as 

 that of the impacts between solids. Whether, however, when the vortex theory 

 of gases is thoroughly worked out, it will or will not be found to fail in a manner 

 analogous to the failure which I have already pointed out in connection with the 

 kinetic theory of gases composed of little elastic solid molecules, I cannot at present 

 undertake to speak with certainty. It seems to me most probable that the vortex 

 theory cannot fail in any such way, because all I have been able to find out hitherto 

 regarding the vibration of vortices,' whether cored or coreless, does not seem to 

 imply the liability of translational or impulsive energies of the individual vortices 

 becoming lost in energy of smaller and smaller vibrations. 



As a step towards kinetic theory of matter it is certainly most interesting to 

 remark that in the quasi-elasticity, elasticity looking like that of an india-rubber 

 band, which we see in a vibrating smoke-ring launched from an elliptic aperture, or 

 in two smoke-rings which were circular, but which have become deformed from 

 circularity by mutual collision, we have in reality a virtual elasticity in matter 

 devoid of elasticity, and even devoid of rigidity, the virtual elasticity being due 

 to motion, and generated by the generation of motion. 



The following Papers were read : — 



1. On the Action of Lubricants. 

 By Professor Osborne Reynolds, F.R.S. 



2. On Kinetic Elasticity as illustrating the Mechanical Theory of Seat, 



By Professor Osborne Reynolds, F.R.S. 



3. On the Vapour-pressure of a substance in the solid and liquid states at the 

 same temperature. By Professor William Ramsay, Ph.D., and Sydney 

 Young, D.Sc. 



Regnault, in the course of his researches on the vapour-pressures of liquids and 

 solids, attempted to ascertain whether the vapour of a substance in the solid state 

 exerted a pressure different from that of the same substance in the liquid state, the 

 temperature being in both cases identical ; and from results obtained with acetic acid, 

 water, and other liquids, he concluded that the vapour-pressure in both cases is the 

 same. Professor Kirchhoff, and independently Professor James Thomson, showed that 

 from theoretical considerations the vapour-pressures must be different ; and the 

 latter, by comparing formulae given by Regnault to express the curves representing 

 very numerous observations on the vapour-pressures of ice and water, discovered 

 a want of continuity in the two curves ; and he pointed out tbat the water-steam 

 curve, if prolonged to temperatures below the freezing point of water, was not 

 identical with the ice-steam curve, experimentally determined by Regnault, aud 

 that the difference approximated to that indicated by theory. 



The authors have experimented with four substances which conclusively prove 

 the justice of Professor Thomson's conclusions, viz., camphor, benzene, acetic acid, 

 and water. With the two first it was proved that the solid-vapour and liquid- 

 vapour curves are not continuous, but would intersect at a temperature close to 

 the melting-point ; and with the two latter they were successful in cooling them in 

 the liquid form below their freezing-points without their solidifying, and in accu- 



1 See papers by the author ' On Vortex Motion,' Trans. R. S. E. April 1867, and 

 ' Vortex Statics,' Proc. R. S. E. December 1875 ; also a paper by J. J. Thomson, B.A., 

 'On the Vibrations of a Vortex King,' Trans. R. S. December 1881, and his valuable 

 book on Vortex Motion (being the Adams prize essay for 1882). 



