r 



622 



REPORT 1884. 



■ I 



.- 



equilibrium. All that I Imvc said in favour o*" tlie modt-l vorlox griis composed of 

 perforated solids with iluid circuliitioiis throu<rh them hnlds wit iiout modification 

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

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

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

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

 analogous to the failure wliich 1 have already pointed out in connection with the 

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

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

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

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

 imply the liability of translational or imp.ilsive energies of the individual vortices 

 becoming h t in energy of smaller and smaller vibrations. 



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

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

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

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

 circularity by mutual collision, we have in reality a v)' Hial elasticity in matter 

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

 to motion, and generated by the generaticm of motion. 



The following Papers were read : — 



1. On the Action of Lithn'r.ants. 

 By Professor O-sboune Reynolds, F.B.S. 



2. On Kinetic Elaatlcit i/ as ilhistraiiiuj the ^[nrhaaical Theor)j of Heat. 

 Bi/ Professor Osisokne Retn'OLDs, F.Ti.S. 



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

 same temperature. Bij Professor William Raji.sav, Ph.D., and Si'DNi:v 

 Young, D.Sc. 



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

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

 exerted a jiressure difl'erent 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 tliat the vapour-pressure in both cases is the 

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

 from tlieoretical considerations the vapour-pressures must be difl'erent; and the 

 latter, by comparing formuhe given by liegnault 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 lie pointed out that the water-steam 

 curve, if prolonged to temperatures below tlie freezing ])oint of water, ,vas not 

 identical witii tlio ice-sieam curve, experimentally determined by Ilegnault, and 

 that the diii'erence approximated to that indicated by theory. 



The authors have experiraenti'd with four substances whicJi conclusively prove 

 the justice of Professor Thomson's conclusions, viz., cam])hor, benzene, acetic acid, 

 and water. With the two lirst it was proved that the solid-vapour and Uquid- 

 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- 



* See papers liy the author 'On Vortex ^fotion,' Trans. It. S. E. April 18G7, and 

 • Vort«x Statics,' Vroc. li. S. E. December 1875; also a paper by .J. ,1. Tliomson, B.A., 

 *On the Vibrations of a Vortex Ring,' Trans. It. S. December 1881, and his vaUiable 

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



