525 
B’ and D’ coincide, then it looks like the diagram of 3 components 
of fig. 2 (ID). When in the diagram of 4 components of fig. 6 (III) 
the curves C’ and £’ coincide, then it looks like the diagram of 
3 components of fig. 6 (II), when B’ and D’ or JD’ and A’ coin- 
cide, then it looks like fig. 4 (II). When in fig. 8 (III) the curves 
C” and B’, or B’ and DP’ or D’ and A’ coincide, then it looks 
like fig, 6 (II). 
We shall call the bundle, to which curve (df) belongs, the (J/)- 
bundle. It is apparent from the previous that this (M) bundle can 
consist either of one single curve [the (J/)-curve]| or of more curves. 
II. Curve (M) is bidirectionable [fig. 2]. 
As curve (M) is bidirectionable, the one part [7a in fig. 2| repre- 
sents the singular equilibrium (4) the other part [7 in fig, 2] 
represents the singular equilibrium (/’,11). As the stable parts of those 
curves (15) and (/,41) go in opposite direction starting from the 
point z, we consider curve a7 to consist of the two curves za and 
ib. In the P,7-diagram of a system of n-components then 2 + 2 
curves occur and not ” +1 curves only as in the case I. 
We see at once that the curve (J/) can never be situated in 
such a way that it is situated between stable parts of curves at 
both sides of the invariant point. In fig. 3 the one part of curve (J/) 
is limited by stable parts of curves, the other part of curve (J/) is 
situated, however, between metastable parts of curves. In fig. 4 
each part of curve (J) is limited at the one side by stable, and 
at the other side by metastable parts of curves. 
We may express this difference in the situation of curve (J/) by 
saying: in fig. 3 (M) is a middlecurve, in fig. 4 (J/) is a limit- 
curve of a bundle. 
When we also here call, the bundle to which curve (J/) belongs, 
the (.J/) bundle, then this consists of two parts. When we consider 
the stable parts only, then it consists in fig. 3 at the one side of 
the invariant point of the (J/)-curve only, at the other side of a 
bundle; in fig. 4 it consists of a bundle at both sides of the invari- 
ant point. 
Consequently we distinguish two cases. 
A. Curve (J/) is a middle-curve of the (J/)-bundle | fig. 3}. 
We find in fig. 8, besides the (J/)-bundle, yet some other bundles, 
viz. P, Q, R and S, of each of these bundles, however, one curve 
is only drawn. 
It follows at once from a consideration of the stable and meta- 
stable parts of the bundles that always a same number of bundles 
must be situated at both sides of the (J/)-bundle. Of course this 
