• i 492 ; 



molecule must collide against il and then it lies in the distance 

 splioro of llial niolecide; and llie considfM-alioiis in which the pressuiv 

 inside llic (hslaiice spheres is assiiiiicil lo he zero, ontsiile thcni to 

 he l\ are c(>rlainlv nol a correcl rcprcseiilnlioii of w hat reall_\ Iinppeiis. 

 Yet poinis \\\\vj: inside dislaiice spheres are in soiiiewhal «liHei'eiil 

 conditions as lo the pivssnre Ihal iiiav he exercised on ihem. Ihaii 

 points outside distance spiieres. li i> nol clear lo me how these 

 conchtions shoidd he taken into ;teeoiinl. It i>. ho\ve\-er. not necessarv 

 lo loiow this in order to cah-nlate the correction term, as will appear 

 IVojii inv secojid ohjeclion. 



in liie second phice the fact has heen overhtoked that not oidv 

 some |>arls of (hslance sphei'(^s he w ilhin other (hstance spheres hnl 

 Ihal the same cii-cnmslance occnrs lor |»arls of the i>oi-(hM-iji,u- snrface. 

 It is iiKJiirerent whether this is an imaizinai'v surface or a solid 

 wall '). in anv case a jiai-t of it will lie w ithin the distance s|)hei-es 

 of the molecules, and mav therefore w ith as mnch lor as little) riuhl 

 he estimated to he |>rolecled from pressiii-e. Now lei 1 / part of the 

 hordering surface lie within the dislance spheres. If w e nnist assnme 

 thai this pari of the surface expei-iences a |)ressure zero, and that the 

 Uvi' sni-face e\|iei-iences a certain pressure, that \\v will call l\, 

 then the (|nanlitv /'. which re|>resents - as ap|>ears from the \>a\ 

 ill \vliich it has heen inli-o(lnced the a\'era,u-e |)ressiii'e, w(MiId he 



(Mjual to . /',. I'Ct ns now inx'estigatc what paiM of the total sur- 

 face of the distance spheres lies within other distance spheres, and 

 let I ^-1 represent that fraction. iIk-ii the aNcrage pressure of a distance 



sphere will amoniit to ' /',. If P., wei-e e(|nal to P.. then the a\ crage 



;., 



[)ressnre on the horderinu' surface and on the dislance spheres wonid 



he the same, and we shonld not ha\-e lo a[)|>lv anv correction to the 



term hy . 



MP 

 •We tiiid the correcli(»n term ^^ * il xve make the follow inu- 



assumption, hiit onlv in that case: every snrface element, — Jio mai- 

 ler whether it is a |>arl of a solid wall or of an ima,uinar\ se|»aratin,i:- 

 snrface, and whether the snrface is |)lane or cni-\ed and no matter 

 whether it lies within nv xxithont the dislance spheres of molecules — 



1) Tlie virial of the tV)roe.s exccrcised by the wall must properly not be integrated 

 over tlie wall itself, but over the surface which contains tlie centers of the mole- 

 cules coUidina- against tUe wall, i. e. over a surface parallel to the Mall and lying 

 at a distance o" from il. 



