32 



JOURNAL OF GEOLOGY— SUPPLEMENT 



series/ It has also been possible to determine accurately the posi- 

 tion of both solidus and liquidus so that the exact composition of 

 solid and liquid in equilibrium with each other in the binary system 

 is known^ (see Fig. 5). The results, given in the paper referred to, 

 show that the liquids are always very much richer in albite than 





 1560 























( 

 1520 



V 



■"■-0. 



















1480 



\ 



\^ 



"^ 



^. 















t440 





\ 



V 





N 



1,, 











1400 







\ 







\ 



\, 









1360 







\ 



V. 







\ 



\ 







1320 









.\ 



\ 







N 



\ 















\ 



5, 







\ 





1240 













\ 







\ 





1200 















\ 







\ 



1160 















N, 



\ 





\ 



1120 

















•SI 



\ 



\ 























^ 



10 



20 



30 



40 50 60 



70 



80 



90 



ANORTHITE 







MOL PERCENT 







ALBITE 



Fig. 5 



the crystals with which they are in equilibrium. In discussing the 

 crystallization of a liquid the consequences of zoning or the sinking 

 of crystals were pointed out.^ On account of the great viscosity 

 of their liquids and consequent ease of undercooling, the artificial 

 plagioclases prepared did not exhibit zoning, being different in this 



' Day and Allen, "The Isomorphism and Thermal Properties of the Feldspars," 

 Carnegie Institution of Washington, Publ. No. 31. 



^ N. L. Bowen, "The Melting Phenomena of the Plagioclase Feldspars," Am. Jour. 

 Sci. (4), XXXV (1913), 583- 

 3 Ibid., p. 597. 



