Ferguson and Merwin — The Ternary System. 177 



formation of an area of solid solution having a minimum 

 width intermediate between the 17 per cent diopside 

 solution and the 5Ca0.2Mg0.6Si0 2 composition. Since 

 the decomposition temperatures of the solid solutions of 

 the akermanite series are but slightly above the inversion 

 temperature of pure wollastonite and much less than the 

 decomposition temperatures of either of the two solid 

 solutions just mentioned, the decomposition tempera- 

 tures of the solid solutions bounding the area running 

 from the 17 per cent diopside solution to the 5Ca0.2MgO. 

 6Si0 2 composition pass through a minimum at this point 

 of minimum width (near F in fig. 2) and thus make pos- 

 sible the two fields of solid solutions which we found in 

 the previous study. 



Solid Solutions tvith Akermanite and 3Ca0.2S%0 2 ' — 

 The optical similarity and fibrous nature of some of the 

 crystals found in charges with compositions lying within 

 the region bounded by the wollastonite-akermanite line 

 and the wollastonite-3Ca0.2Si0 2 part of the side line 

 rendered any direct determination of homogeneity upon 

 charges crystallized at low temperature impossible. An 

 investigation of the inversion and decomposition temper- 

 atures within this region seemed also futile and therefore 

 no definite results were obtained with such compositions. 

 The only means available for determining if pseudo wol- 

 lastonite solutions extend across this region was a study 

 of the temperatures of complete melting similar to that 

 carried out upon the compositions between the diopside 

 and akermanite lines. Experiments were here not car- 

 ried out as the liquidus relations previously obtained in 

 no way indicated the existence of two pseudowollastonite 

 fields. We think it probable that both the wollastonite 

 and the pseudowollastonite solutions extend to the side 

 line in this region. 



Discussion. 



The liquidus-solidus relations of these various solid 

 solutions were but briefly mentioned in the previous 

 paper and a more thorough discussion will now be given. 

 For this purpose, we have reproduced with a little more 

 detail in fig. 2 that part of fig. 1 which dealt with these 

 solid solutions, but omitting, because of the scale of the 

 drawing, several minor parts 14 which would have to be 



14 Thus we show no solid solution of pseudowollastonite beyond the diopside 

 line toward silica. (See p. 173.) 



