825 



Consequently we may consider the solid as a monoconcave 

 octohedron, which is composed of the tetrahedrons EABD and 

 CABD, diminished with FBCD; these tetrahedrons terminate again, 

 the same as in the tigs. 1 and 3 in the side BD. 



/^^-^ 



Fig. 5. Fig. 6. 



In order to define the position of the curves with respect to F' 

 and E' , we consider the hexahedron EABDC and the tetrahedron 

 ABCD, within which the point F is situated. We find : 



C'E'\F'\A'B' D' (9) 



and A'B'CD'\E'\F' (10) 



Now we draw again in a /^ T'-diagrain the curves F' and E' 

 (fig. 6) and we take again E' at the left of F' . 



In this connection (9) and (10) have been written at once in such 

 a way that also herein E' is at the left of F' . 



It follows from (9) and (10) that t" must be situated at the left 

 of F' and of E' \ consequently C' must be situated within the 

 angle, which is formed by the stable part of E' and the inetaslal)lc 

 part of F'. 



Further it is apparent from (9) and (10) that A' , B' and Ü' must 

 be situated at the right of F' , but at the left of E' \ conseqiienily 

 they are situated, as is also drawn in fig. 6 within the metaslable 

 parts of E' and F' . 



Now we have still to detine the position of the three curves A', 

 B' and D' with respect to one another. From the tetrahedron 

 CBDE within which the point F is situated, it follows: 



F' I A' I B'C'D'E' (11) 



so that at the one side of A' only F' , at the other side B' , C", D' 



53* 



