280 H. S. Summers : 



1. Limburgite - Average of 5 analyses. 



2. Woodenite - (Complementary). 



3. Anorthoclase Basalt - (Complementary). 



4. Mac«donite - (Complementary) 



5. Blend of Complementary Types. 



6. Blend of Alkali types less acid Trachyte and Solvsbergite. 



7. Olivine anorthoclase Trachyte (Cobaw Type) 



8. Anothoclase Basalt - (Complementary). 



9. Macedonite - (Complementary). 



-10. Anorthoclase Olivine Trachyte - (Sugarloaf Type). 



11. Blend of Alkali Rocks. 



12. Anorthoclase Trachyte - Average of 4 analyses. 



13. Solvsbergite - Average of 3 analyses. 



Variation diagrams based on these recalculated analyses are- 

 given in Fig. 5. The curves obtained are in general better than 

 those plotted from the original analyses (compare with Plates 

 VII. -IX.. Bulletin No. 24, Geol. Surv. of Victoria 1912). 



The differentiation of the Kainozoie alkali lavas of Macedon has 

 been discussed in some detail (19), but some additions to tliis 

 discussion may be included here. 



In the first place, judging from the variation diagram (Fig. 

 4), differentiation must have proceeded on different lines to those 

 exhibited by the dacite-granitic series. In the latter case variation 

 could be expressed by straight lines, but the variation of the alkali 

 rocks must be expressed by curves. It has been pointed out above 

 that the molecular concentration of the Palaeozoic rocks remained 

 constant throughout the differentiation. 



In the case of the rocks under consideration, however, this is 

 not the case. The molecular ratios are set out in Table XIII., the 

 order of the analyses being the same as in the preceding table. 



Total - 1.597 1.600 1.544 1.502 1.539 1.536 1.628- 



