( 798 ) 



velocity which is best seen bv iiDagiiiiii.u a central shock, in which 

 !)Oth iiiolccules pursue Ihcir way iii the direclioii from wliicli lliey 

 came, but adopting each other's motion. It is tliereforc Just as if 

 they have passed through eacii other with infinite velocity and as 

 if further nothing has happened, so also as if the quantity of motion 

 — of whose motion the pressure of the gas is a consequence — 

 does not move with Ihe velocity of the molecules, but as if with 

 every mean path which is described, a distance is saved, which is 

 a mean of the distances of the centres of the molecules in collisions. 

 If the distance obtained iji this way is Vs •'>*K 2 for every mean path of 



— =: , tlieJi the increase of the pressure is : 



1/2 ;j ns^ ' — 1 I '' 



V V 



\/2 mis'" 

 If the mean path, \vheu we take into consideration that the 



V /A 



«Hstance spheix's cover each olhei-, is — 1-?, where (■? = </5 



^ V/2 nm' \< 



h 

 tiien the factor which we must take into account is 1 -| — Z^, and 



V 



we get the strictly accurate ecpiation: 



a\ RTf b \ 



"+,..;= t('+ 7 'V *'' 



The train of thougiit whicii we ha\e sketched here in a few 



words, and from which (t. J.uiKU (loc. cit.) arrived for the first time 



/ -öh\ 

 at the correctiou term l>^.=zh\ l + o ' ) ^'^^^ already l)een rigorously 



developed by Koktkav K(; '), but he seems to have come to another 

 result. This (bsagreemciit is, however, only seeming. Kokteweg 

 says"): "the siini of all the distances sa\ed by collisions is therefore 

 A: A Tr cos i- <]r'). The sum. howexer, of all the distances witli which the 

 r niolecides apj»roacli the plane All in ihc time <lt is evidently 

 Pr cos f (I/.' 



Now it is beyond doubt in my o[)iuioii, that if a number of mole- 

 cules in the time <// \)\ tiieii' own velocity pass over a way A' cuv f r/^, 



1) Verslagen der Kou. Ak. AtU. Naluurk. Tweede reeks X p. 'ói?!. 

 ^) I. c. ].. BCD. 



'^) A = - ill Diir In iiiiiiojouv : /• reiirosriits: llic velocilv of the molecules ill 

 ■ir 



KuuTEWEci'b paper. 



