560 THE DISTRIBUTION, ETC., OF ALKALINE ROCKS, 



1. Blowhole Flow basalt, a basic flow; magmatic name Andose. 

 Total alkali, 5*94 per cent. 



2. Bumbo Flow; magmatic name Shoshonose and Monzonose 

 (orthoclase basalts). Total alkali, 7-89 to 9*19 per cent. 



3. Saddleback Flow dolerite; magmatic name Andose. Total 

 alkali, 5*96 per cent. 



4. Cambewana Flow trachyte; magmatic name Monzonose. 

 Total alkali, 9'37 per cent. 



5. Minamurra Flow ; magmatic name Camptonose. Total 

 alkali, 7*28 per cent. 



6. Bong-Bong Flow of alkaline basalt; magmatic name Andose. 

 Total alkali, 4*79 per cent. 



All the foregoing flows are of Permo-Carboniferous age. 

 Lastly we have — 



7. The Robertson Flow of Post-Triassic basalt. Total alkali, 

 3*33 per cent.; magmatic name Auvergnose. This rock contains 

 analcite and is closel'y related to the basalts intruding theTriassic 

 rocks of the Sydney Basin (eg., the Prospect mass). 



The intrusive rocks of the Kiama-Jamberoo district comprise — 



1. Nepheline syenite, later than Permo-Carboniferous. 



2. Dhruwalgha tinguaite, Post-Permo-Carboniferous; a rock 

 containing nepheline, sodalite, arfvedsonite, barkevicite, segirine, 

 etc.; magmatic name Laurdalose. 



3. Wallaya dolerite, a basic intrusive sheet in the Permo- 

 Carboniferous. 



4. Dykes of monchiquite, dolerite, ophitic dolerite, olivine 

 basalt, and trachyte. 



While the data given by the authors are not quite complete 

 enough to permit of the working out of the minute details of the 

 magmatic differentiation which has taken place here, as Brogger 

 has done for the Christiania rocks, the conclusions arrived at by 

 the authors are nevertheless of the highest interest and import- 

 ance. They are in fact of the opinion that in early Permo-Car- 

 boniferous times, or perhaps earlier, a great mass of very basic 

 rock invaded the earth's crust of this area. By stoping in and 

 assimilation the invaded rocks, which must have been of a highly 



