( 463) 
part has been covered by the sides which approach each other. If 
we now think this deformation exceedingly slight at the top, but 
strongly increasing when moving from the top, then the character 
of the plaitpoint remains almost unaltered at the plaitpoint, but far 
from the top a sharp crevice is substituted for the gently sloping 
part between the two side-walls. In this we have only wished 
to represent the shape for that part of the ¢-surface which is visible 
to an eye placed under it. 
If we want to imagine a deformation of the plait, which leaves 
the other parts also in existence, we should have to apply four 
folds originating in the point A, of which the two outer folds brought 
together would have to represent the line of the coincidence pres- 
sures, and the two others would form the series of cusps. But in this 
way we do not account for the fact, that (fig. 3) the left-side points 
E and D' belong to the right-side point &' and vice versa. 
At all events it is clear that the name “plait” for a such a 
configuration might give rise to a great deal of misunderstanding, 
unless we take care to distinguish it by an adequate addition. We 
might, e.g. speak of a plait of three sheets. 
If we pass now from the geometrical treatment to the question 
what the science of physics may derive from it, we can summarize 
the answer in the thesis: the critical phenomena ofa ternary system 
are equal to those of a binary system. At the chosen temperature 
all the mixtures indicated by the course of P are under the 
plaitpointcircumstance. (fig. 6). The plaitpoint pressure alone varies 
for all those different mixtures. The limiting value of Ee is 
0 — fi 
indicated by the direction of the tangent in P at the connodal curve. 
The mixtures which are in the point-of-contact circumstance at 
the chosen temperature, are found by means of the envelope of 
the different binodal curves, and that of those branches of these 
curves which lie on the side of the hypothenuse of A OAB, 
The mixtures indicated by points lying between the locus of P and 
that of the before-mentioned envelope have retrograde condensation, 
and in accordance with the suppositions made in fig. 2, retrograde 
condensation of the first kind. 
It has not been my purpose in the preceding pages to examine 
the different cases which may occur for a ternary system. But it 
has been my purpose to demonstrate in what way they may be 
explained by means of the ¢-function, when for some cause or other 
they will have come more to the front, 
