TUANSACTIONS OK M:( TIO.N A. 



61 



to priivf wliiilly futile r l!iit, now, iiistcail nf imii^;iiiiiij,' tin' ((in'slion : Wliiif i\<i 

 villi iiH'ftn by fxpliiiiiini; a ]>iiiperty "f iniitlfi!-' in he put cyniciilly, iiiul It-ttiii;:- 

 oiirHclvt'S 1m' irritftfi'il by it, «uppi)Nc we ^:ivo tn tlin (|ut'stiiin<'r ciwlit for licini.' 

 >viii;)ntht'ti(', nud condf.sLentl to try iimi iiuswor lii^ (picstioii. \\'t> titnl it iini very 

 (•ii.«'V to di) HO. All tlu' inopfrtit'.s of niiitttT iirc .>ri couni'dfil tluit wo cnn Hciirccly 

 iimi^'ini' oiii' thnriiinihli) i ip/diiitd williout our sci'iujr its iflation to all the otbcr>, 

 without in fad havinjr the explaiiatiou of all; and till we have this we cannot tell 

 what we mean by ' explaininjr a propoity,' or 'exi>lMinin>,' tlu; properties' of matter. 

 Hat thi)ii;.'li this con-uiuuuition may never be reacluKl by man, the pr. f^ress of 

 .Hcience nuiy be, I lielie\o will be. step by stej) towanls it, on many ditferent road^ 

 (■iiiiviM'fjinfj towanls it from all .«<ides. Tiie kinetic theory of pises is, as I have sai<l, 

 n true step on oiu; of the roads. On the very di.*tiuet road of eiieminil scienee, 

 St. Clair Devillu arrived at his j.'rand theory of dis.soeiation willwuit the sliffhte>t 

 nil! from the Idnetic theory of j?ases. 'I'lii! fact that he W(U'ke<l it out solely fron» 

 ilieiiiical ol)servati(>n and experiment, and ex|iounded it I'l the wiu'ld without any 

 li\|>othesis whatever, and seeiuin;^ly even without consciousness of thtf beautiful 

 cxiilanation it has in the kinetic theory of pises, secured lor it iinme<liately an 

 iiule|iendeiit solidity and iniportaiice as a chemical theory when he first promul- 

 ;^iited it, to which it mij-dit even hy this time scaicely have attained if it had lirsi 

 hceii su;rp'sted as a jn'obability indicated by the kinetic theory of jrases, and been 

 only afterwards contirmed by observation. Now. however, guided by the views 

 uhich ("hiusius and Williamson have jjriveii us of the continuous interchanp' of 

 partners between the compound nudecules const itutiii;j: chemical compounds in the 

 ;;aseoiis state, we see in Meville's (lieorv of dissociatiiui a ])oint of contact of the 

 must transcendent interest between the cheiiiicai and physical lines of scientitic 

 profjfress. 



To return to elasticity : if we could make out of nnitter devoid of elasticity .1 

 combined system of ndatively moviii;r I'nrts which, in virtue of motion, has the 

 essential characteristics id' an elastic body, this would surely be, if not positively 

 n step in the kinetic theory of nuitler, nt least a liiiL'er-post ))oiiitin).'- a way which 

 we may hope will lead to a kiiu'tic tlie(U'y ofniader. Now this, as I have already 

 .-liowii, ' wf can do in several ways. In the case of the last of the comnumications 

 referred to, of which oidy the title has hiiherto been publislied, I showed that, from 

 the mathematical invest iirat ion of a f,i-yrostaticiiily dominated combination contained 

 in the passap! of Thomson and Tait's ' Natural IMiilosophy ' referred to, it follows 

 that any ideal system of material particles, actinjr on one another nnitually through 

 niassless connt^cting sjirings, may be ])erl'ectly imitated in a model consisting of 

 rigid links jointed together, and having rapiilly rotating fly-wheels pivoted on 

 some or on all of i\n' links. The imitation is not contined to cases of e(juilibriuni. 

 It holds also for \ibration jiroduced by disturbiiej; the .system infinitesimally fnun a 

 position of stable eipiilibrium and leaving it to itself. Thus we may nuike ii 

 gyrostatic sy.stem such that it is in etniilibriuni under thi! intliience of certain 

 jiositive forces ajijdied to ditlerent ]> )ints of tiiis system ; all the forces being 

 precisely the same as, and the points of a|)]ilicatiun similarly sitiiateil to, those of the 

 stable system with sj)rings. Then, provided jiroper nnisses (that is to sny, proper 

 amounts and distributions of inertia) be attributed to the links, we may remove 

 the external forces from each system, and the conse((ucnt vibration of the points 

 of applicatioi- of the forces will be identical. Or we may act upon t!ie systems 

 of material points and springs with any given forces for any given time, and leave 

 it to itself, ami do the same thing for the gyrostatic system; the consequent 

 motion will be the same in the two cases. If in the one case the springs are 

 made more and more still", and in the other case the angular velocities of the fly- 

 wheels are made greater and greater, the periods of the vibrational constituents of 



' I'apcr on ' Vortex Atoms,' Pror. 11. S. IL Teb. 1 SO? ; abstract of Lecture before 

 Iioyal Institution of (Jreat Britain, March 4, I«Sf, on * Klasticity viewed as possibly 

 a Mode of Motion ; ' Thomson and Tait's Nafiiral Philunophy, second edition. Part I. 

 <>§ ;J45 viii to 34") xxvii ; 'On Oscillation and \\:ives in an Adynamic Gyrostatic 

 System ' (title only), I'ror. It. ,S'. K March 1S»:!. 



