338 EEE VOGL 
T100°), consequently with a difference of ca. 200° between the 
two points. 
For the analogous system Qu:Ab:An, where the difference 
between the two points (Egu-an at -1350° and Egu-ap at probably 
a little below 1000°) is still greater, certainly at least 350°, we 
may also suppose a continuous decline for the eutectic line. This 
line, on account of the steep decline near Ab of the binary liquidus 
curve between An and Ab, will probably assume the course outlined 
on the horizontal projection, Figure 5. The crystallization be- 
tween Ab+ An and Qu has consequently the same course as between 
Ab+An and diopside (see below). Even if the curve between 
Eou-an and Egu-ap, contrary to our conjecture, should show a 
maximum in the vicinity of Egu-an or a minimum in the vicinity 
of Eou-ap, this would in no degree worth mentioning modify the 
course of the curve in the horizontal projection. 
We calculate the chemical composition of the end members and 
of a pair of intermediate compositions. 
TABLE III 
EQu-Ab+An by 
Percentage of EQu-Ab ee EQu-An 
= Ab:} An 2 An:3 Ab 
Quay Mane teres 28 30 42 48 
{Ab 72 48 20) ikea ea 
sce aVa Beatin ot Ale doll Bedell Hi 8 cape aie 16 209 52 
SiO ate Dh AS 75-95 74.5 70.5 
NIE Ores Acetate b 13.95 i 52 16.25 19.0 
CaO ecg se Sema ceenta a BoB 5.85 10.5 
Nat © eeeniie 8.50 5.65 2.4 |) Ge 
That the calculation here given of the eutectic between quartz 
and albite, oligoclase, etc. (which is supported by the theoretical 
argument on the eutectic Qu: An at the pressure of one atmosphere, 
and by analogy conclusions according to the composition of micro- 
cline graphic granite) is essentially correct, is confirmed by the 
close conformity between the two analyses, Nos. 12 and 13, of 
oligoclase graphic granite and the compositions here calculated, 
especially for 2 Ab:% An. 
For the system Quartz:Orthoclase (microcline, with about 
72 Or+28 Abian):Albite (with about 88 Ab or Ab+an and 12 Or) 
we must have three individualization-fields, with partial eutectics 
