BY D. MAVVSON. 581 



After a careful study of a number of sections representing 

 stages from the completely carbonated rock to the freshest 

 obtainable, I am able to state that the original iron silicates were 

 tegirine and segirine-augite. Exceptionally, traces of blue amphi- 

 bole were observed, but evidently derived by uralitisation from 

 the segirine. 



The felspar is a clear orthoclase and has evidently preceded 

 the segirine in crystallising out. In fact the ferriferous silicates, 

 in the main, occupy what were minute drusj?' cavities, fairly 

 evenly scattered, left after the complete crystallisation of the 

 felspar; the latter has taken effect in such a way as to form 

 compact areas between the residual drusy spaces. These compact 

 felspar areas, though presenting idiomorphic boundaries towards 

 the cavities, have internally a moire appearance. 



In distinction to this type of solidification, producing solid 

 felspar aggregates and free areas between occupied by the ferri- 

 ferous residuum of the magma, is the typical paisanite* from the 

 summit of Mt. Jellore, eight miles to the north-east, in which 

 spongy felspar crystallisations have resulted, with interspaces 

 occupied by a poikilitic arrangement of later crystallising 

 amphibole. 



The Bowral syenite is unique in forming so huge an intrusive 

 mass and still remaining so even-textured and fine-grained; it is 

 completely crystalline and shows no attempt at flow structure. 



The general characters of the rock are more those of an aplite 

 than of a typical syenite, but, on account of its field relations, 

 must be considered with the latter. 



Originally containing a considerable proportion of pegirine and 

 related pyroxene, it can no longer be regarded a bostonite, and 

 naturally is to be considered with the class of gegirine-syenites 

 described by Rosenbusch.f Comparison of the analyses j with 

 that of the a'girine-syenite from Salem Neck§ makes the analogy 

 more apparent. 



* hoc. cit., compare figs.l and 2 of Plate xxvi. 



t "Eleniente der Gesteinslehre," 1901 Ed., p. US. 



X " Geology of Mittagong," Analyses ii. and iii., p.341. 



§ " Eleniente der Gesteinslehre," Anal. 15, p. 114. 



