826 



and E' must be sidiated. Conseqiienlly curve A' is sidiated as is 

 drawn in fig (i. 



The contemplation of the iiexahedron EABDF gives us: 



E'F' I C' I A'B'D' (12) 



but it does not teach ns anjtiiing new. 



Now we have still to define the position of B' and 1)' with 

 respect to one another, we shall refer to this later. 



When we summarize the obtained results, we niaj saj : 



when the six phases form the aiiglepoints of a monoconcave 

 octohedron, then the six nionovariant curves form in the P, T- 

 diagram one threecurvical, one twocurvical and one onecurvical bundle. 



Type IV. In fig. 7 the six phases form the anglepoints of the 

 tetrahedron ABCD, within which tiie points E and F are situated. 

 The line EF intersects the triangles ABD and CBD; now we 

 unite E with A, B and D and also F with C, B and D. Conse- 

 quently we may consider the solid as a biconcave octohedron, which 

 is composed of the tetrahedron ABCD, diminished with the tetra- 

 hedrons EABD and FCBD. These three tetrahedrons terminate 

 again in the side BD. 



From the position of the five phases of the equilibrium F' with 

 respect to one another we find : 



E' \ F' \ A'B'C'D' (13) 



It follows for the position of the equilibrium E' : 



A'B'C'D' \ E' \ F' (14) 



Now we draw in a P, 7-diagram (fig. 8) again the curves F' and 

 /'J' and we take again E' at the left of F' . in accordance with this 

 also in [1?-) and (14) E' is taken at the left of F' . 



Fig. 7. 



