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refer as the first in our further considerations, yields a critical line, 
which consists of two entirely detached portions, one of which, lying 
at high temperature, presents the normal shape, and the other is in the 
P,T-projection a closed figure with two heterogeneous double plait- 
points, which represents the locus of the critical points of the longi- 
tudinal plait. 
In the second place it is possible that the Jongitudinal plait, which 
has got outside the transverse plait in the same way as above, 
continues to exist far above the temperature at which the transverse 
plait gets detached on one of the two sides. Then a transition takes 
place at a certain temperature in the connection of the plaits; the 
longitudinal plait, which was entirely closed at low temperature, 
then merges into a part of the transverse plait, while simultaneously 
the portion of the transverse plait on the side of the component with 
the lower critical temperature gets isolated, and retreats inside the 
former at rise of temperature, and disappears. This case is referred 
to as the second in what follows. 
I have now examined the question what phenomena may appear, 
when a tangent plane for solid-fluid is rolled over the w-surfaces in 
question, and it has appeared to me that the behaviour in both cases 
can be ascertained by a comparatively simple train of reasoning. In 
these considerations | have confined myself to those cases, for which 
only the components occur as solid substances. 
3. The first case. 
When we consider the case that was called the first in the pre- 
ceding paragraph, we can get a survey of the phenomena by means 
of figure 1. In this figure it has been assumed that (dp/dz), is always 
positive, in other words that we are in the lefthand part of tbe 
isobaric figure. The longitudinal plait here possesses two critical 
points P, and P, where contact takes place with the spinodal line. 
Further only the liquid binodal line has been drawn of the transverse 
plait; the vapour branch, which lies at large volumes has been 
omitted in the diagram; it possesses a ridge, the two end-points of 
which indicate the phases coexisting with A and 4. About the rela- 
tive situation of longitudinal and transverse plait we know that at 
low temperature the longitudinal plait lies entirely inside the trans- 
verse plait, at higher temperature the former passes the border of 
the transverse plait, and at still higher temperature it retreats again 
inside the latter. In this temperature range the transverse plait covers 
the whole width of the figure, as we remain all the time below the 
critical temperature of the components. 
