Diopside — Forsterite — Silica. 



223 



Since the points N and 1ST, represent the composition of 

 liquids in equilibrium with two solid phases they evidently 

 would lie on the boundary curve DE of fig. 8. From each 



Fig. 10. 



Fig. 11. 



point along the boundary curve lines corresponding with NK 

 and N 1 K 1 and with NC and T$fi may be drawn. A set of 

 these lines is shown in fig. 10. They are the three-phase- 

 boundaries for various temperatures and indicate the composi- 



