( 548 j 
question as to the possibility of these cases. But I shall not. enter 
into this subject at least for the present. 
Between the two closed parts of which the projection of the con- 
nodal curve on the zy-surface consists, lies another closed curve, the 
projection of the double points. The curve, which consisted of one 
branch in the case discussed on page 460 within the triangle OAB, 
consists in this case of two branches lying within the triangle. At any 
rate it will always consist of two branches theoretically; but for the 
¢-surface we need only to know that part which lies within the 
triangle. When p has the value of the before-mentioned maximum 
pressure, the closed curve of double points too contracts to one point. 
This point is the same as that to which the two closed parts of the 
connodal curve contract. 
If for a moment we take recourse to molecular-theoretical consi- 
derations to derive properties of the locus of the double points, we 
should write down the equation of p. 461 in this way: 
In this equation which holds good at least as an approximation, 
Lia Le 8 
a7 oi ora ap 
Keeping 7 constant, we get by differentiation: 
BREE é oe 5) B G-5) 
we put f= constant and pe = 
p a b T Xe b 
or 
rn: Sl Eje. 
p dk b th a 
Keeping p constant we find the condition: 
da Ji 
RET. matiek sige 92 
EN i de 
dba aod oracles : 
— =a 
b I? 
In the limiting case, for continually decreasing values of “7, the 
value of the second member — 1, and so: 
-(= dy 2) zi dy 5) 
a\de | de dy ES Ow de oy 
