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Physics. — Dr. .1. K. Vkksciiaffklt : I'Coiitrilnitions to the knoirlrdii,' 

 of VAN derWaat.s' Vi^-.surfac.e\\\. The equations of sfxf,' and 

 ihc \\-x}irfi(C(' ill the immediate i)ei(//d)07fr/tood of the crilical 

 slate for Itiiinnj iiiixtvres iridi a small /iro/iortioii of one of 

 the eompoiieiits.'' {part 3)'). (Siipplciiiciil N". (i to llic ('oni- 

 nmiiicalioii fVoiii llic Physical Lal)()rat()i-y al Loideii l)\ Vvoi'. 

 KA:\iF,RT,iN(iii Onnks). 



(Comniunicaled in tlie meeting of Kebr. 28, IIKK}.) 

 1.5. 77/^' \]--siiifare in t/iei)innediatenei(//i/iinrr/ioodofthei>iait/)oinf. 



]\\ ihc appliratio]!, after Kkesom^), of K()rtkwe(i's in-qjective traiis- 

 foi'Hiation ") to the e(|natioiis of (he if'-siirface, I have expressed llie 

 ('oefficiejits (»f my equation (20) in terms of tliose used by Koktkww; 

 to study tiie plait in the paper mentioned. 



The followin*;' new coordinates must he iidroduced 



tf." -^ (i!'-i|T./ ) - ir'-rr,i ) (^^) - (.r-.VT,i ) f"^) . 



x" — {.v. — xTpl) — m {i' — VT,.l)' 

 ?•'■ = v—VT/,!, 

 where m is determined l)y the e(piatio]i 



dhp\ / dh]^\ _ 



to the first approximation and by the use of equation (20) this i-educes to 

 Since the equation of the <|'-sui'face contains a term with I<i</ .v, 



^^0 1 

 VI == .?: 



RTk '^' 



1) Proc. Amsterdam. 28 June and 27 Sept. 1902. 

 ~) Proc. Amsterdam. 27 Sept. 1902, p. ^il. 

 ••) Wien. Ber., 98, 1159, 1889. 



-^) In agreement with Keesom's expression (i.e. p. 342). The value of m must 

 also fulfil the two other equations: 



\0.vdv jTpl \0v^ Jt,A 

 and 



-. . , +^m-l —-V + 3 m —^ +^^1=0; 

 0'^ Jrpl \oa"-dvjTfjl \d.cdvyTpl \OvyTj>l 



this is really the case when the above values of Xvpi and VTpi are substituted. 

 Conversely we can use these equalions to determine X/y and rr,,/, as Kor»TK,\VK(.i 

 has done. (Proc. Amsterdam. 'M Jan. 190:3, p. Ö2G). 



