898 
It is self-evident that the total attractive force will become = 0 
somewhat earlier, when P moves towards M,, than at 6, (when 
F, acts alone) — it does so at o', or simply o’ — because the 
attractive force of JM, acts in opposite sense. In fact the above 
quantity becomes = 0, when 
tt = V (l—s)* — (gs) (6 —s8) = V (l—o)* — (0 +. o—2l) (o—s) = lo’ 
As in the case under consideration the molecule P will always 
be within the spheres of attraction of the two molecules M, and M,, 
2l is always <o-+s, hence a fortiori U <p + 6 (cf. p. 1187 Lc). 
The value of z, is therefore < ]—o, i.e. F becomes — 0 in 0’, 
on the left side of 6, *). 
However, all such functions have the drawback, that the further 
integrations become impossible to carry out by means of closed 
forms; for both at high and at low temperatures (u, large or small) 
x 
the term of work "nf in Ve Deen Fdx can never be con- 
sidered as permanently small with inci to wu,” between the limits 
«= 0 and «=s’. For in the end (at the culmination point of the 
collision) the quantity under the sign of the root becomes = 0 in 
both cases (high and low temperature), hence the term of work 
under consideration of the same order of magnitude as w,*. And at 
low temperatures, which is justly the most important case in our 
considerations, that term is almost everywhere of the order of 
magnitude w‚* — except in the neighbourhood of the points O and 
somewhere between o’ and s’, where this term becomes = 0 (Cf. 
Fig. 3). 
For this reason we were obliged in our first paper to consider 
the attraction and the repulsion separately, and to assume, instead 
of the course of F drawn in Fig. 3, a force which continues to 
increase in direct rativ to w as far as o,, after which it suddenly 
changes into a repulsive force, which likewise increases linearly as 
the distance from P to 6, (P now thought on the righthand side 
of 6,). This renders the integrations easy to carry out, and does not 
touch the nature of the matter. 
If it is thought desirable to avoid the introduction of a so-called 
“sphere of attraction” — which at the same time offers the advan- 
1) When the distance 7 of the molecules becomes too small, F will not first 
become positive on the righthand side of O, become =O in oc’, and then negative 
— but at once negative, i.e. there is already immediately repulsion on the right- 
hand side of O. The same thing applies of course to the left side. We shall 
return to all these different cases in our next paper on the calculation of the Virial. 
