MAGMATIC DIFFERENTIATION OF IGNEOUS ROCKS 337 
Qu:Ab+An.—In a ternary system consisting of two components 
(as, for instance, Ab and An), which form a binary mix-crystal 
system of type I, and a third component independent of the former 
(as Qu or CaMgSi,0¢), there appear, according to F. A. H. Schreine- 
maker’s theoretical investigations,’ two melting-surfaces (Fig. 4), 
Tou 
ca. 1675° 
Qu 
Fic. 4.—The ternary system An:Ab:Qu 
which intersect in a curve, viz., ‘‘eutectic boundary-line’’? or 
briefly a “eutectic line or curve.” Three subcases may occur, 
accordingly as the eutectic boundary-line (Equ-an to Equ-ap on 
Fig. 4) has a continuous decline, a minimum, or a maximum. In 
the ternary system Diops:Ab:An the eutectic line according to 
Bowen’s experimental investigations (see Fig. 6) has a continuous 
decline from Epjops-an (at 1270°) to Epjiops-ap (at a little below 
t Zeitschr. f. physikalische Chemie, 1905, Vols. 50, 51, and 52. 
2 This term I have used in my earlier treatise. Boeke (loc. cit.) uses the shorter 
term “‘eutectic line.” 
