THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. VII.— The Ternary System CaO-MgO-Si0 2 ;by J. B. 

 Ferguson and H. E. Merwin. 



Contents. 

 Introduction. 



Previous investigations: Temperature relations and optical properties. 

 General procedure and apparatus. 



The crystalline phases: Composition, optical properties, etc. 

 Fields of stability. 



Temperature relations along the boundary lines. 

 The quintuple points. f 



Melting temperatures within the .fields. 

 Discussion of the fields. _^\Y\SO^ ttn ,ri '* 



Pseudowollastonite, wollastoilite, 5Ca0.2Mg0.6Si0 2 , diopside. 



Monticellite solid solutions. 



Akermanite. f «rt . , n ^ 



The tridymite-eristobalite inversion. I » j\\j Q ~j 



The binary systems within the ternary systemV . 

 Summary- \ *W* t 



Introduction. ., ^^^ 



A number of investigations dealing with one or more 

 of the four oxides, lime, alumina, magnesia and silica, 

 have in recent years been carried out as preliminary 

 steps in the laboratory study of rocks. To the results 

 of these investigations which dealt with the three ternary 

 systems, CaO-AL0 9 -Si0 2 , CaO-MgO-Al 2 3 , MgO-Al 2 3 - 

 Si0 2 and parts of the fourth ternary system, CaO-MgO- 

 SiOo, we wish to add the results 1 of an investigation of 

 the hitherto unknown parts of this last system and also 

 to correlate these results with those previously obtained 

 by others. Since but four ternary systems may be con- 

 structed from the four oxides, this investigation marks 

 the completion of the series of studies of the solidus- 

 liquidus relations in these ternary systems. 



1 A short preliminary summary of these results was published in Proc. 

 Nat. Acad. Sci., 5, 16,' 1919. 



Am. Jour. S C i.— Fourth Series, Vol. XLVITI, No. 284.— August, 1919. 



