Ferguson and Merwin — The Ternary System. 113 



The phase CaO.MgO.Si0 2 is unstable at its melting 

 point and in addition is variable in composition since it 

 belongs to a series of solid solutions of forsterite in pure 

 monticellite. 











Table 



XIX. 







Melting temperatures within the monticellite field. 













Time 





Composition 

 CaO MgO 



wt 



Si0 2 



Temp. 



°C. 



in 

 min. 



Phases present 



33 



25 





42 



1502 

 1509 



16 

 16 



Glass -j- crystals 

 Glass 



35 



22 





43 



1478 



15 



Glass 



37 



21 





42 



1473 

 1483 



15 

 15 



Glass -j- crystals 

 Glass 



37 



22 





41 



1467 

 1497 



15 

 15 



Glass -j- crystals 

 Glass 



38 



20 





42 



1487 

 1489 

 1483 



15 

 18 

 15 



Glass -j- crystals 



Glass 



Glass -f- crystals 











Table XX. 





ig temperatures within the periclase field, the 



2800 ± 20°C. 



melting point of pericl 













Time 





Composition 

 CaO MgO 



wt. 



Si0 2 



Temp. 

 °C. 



in 

 min. 



Phases present 



34 



25 





41 



1515 



20 



Glass -j- trace MgO 



35 



25 





40 



1539 



10 



Glass 



37 



23 





40 



1528 

 1521 

 1517 



Table ■ 



10 

 20 

 20 



XXI. 



Glass -f- crystals 



Glass 



Glass -f- crystals 



Melting temperatures within the forsterite fiekl, the melting point of 

 forsterite 1890 °C. 



Time 



Composition 



wt. % 



Temp. 



in 



Phase presented 



CaO MgO 



Si0 2 



°C. 



min. 





24 24 



52 



1432 



10 



Glass 







1426 



10 



Glass -J- trace crystals 



23 28 



49 



1528 



10 



Glass -f- trace crystals 



27 26 



47 



1501 



15 



Glass -j- crystals 







1509 



15 



Glass 



28 24 



48 



1460 



10 



Glass -f- crystals 







1468 



10 



Glass 



30 25 



45 



1490 



15 



Glass 







1485 



15 



Glass -J- crystals 



32 23 



45 



1459 



15 



Glass 







1445 



20 



Glass -f- crystals 



32 25 



43 



1498 



15 



Glass -[- trace crystals 



32 26 



42 



1506 



20 



Glass -j- crystals 







1510 



20 



Glass 



Am. Jour. Sci.— Fourth Series, Vol. XLVI1I, No. 284.— August, 1919. 

 8 



