[Pboc. Roy. Soc. Victoria, 21 (N.S.), Pt. I., 1908.] 



Art. X. — On the Evidence of the Origin, Age, and 

 Alteration of the Rocks near Heathcote, Victoria. 



By ERNEST W. SKEATS, D.Sc, A.R.C.S., F.G.S. 



(Professor of Geology in the University of Melbourne). 



(With Plates XIV.-XVIII.). 

 [Read 11th June. 1908]. 



1. — Introduction- -..-..- 303 



2. — Previous Literature ------ 304 



3. — Discussion of previous work. - - - - 310 



4. — Relations of the Igneous Rocks to the Silurian 



Series .-.---.- 315 



5. — Relations of the Igneous Rocks and Black 



Cherts to the Ordovician Series- - - 316 



6. — Relations opthe Dinesus Beds to the Ordovician 



AND to the Diabase . . . . . 322 



7. — Nature and Origin of the Igneous and 



Pyroclastic Rocks 323 



8. — Nature and Origin of the Ordovician Sediments 329 



9. — Altered Rocks — 



A — The Cherts and their mode of origin - 330 



B — Abnormal Characters of the Diabase Series 

 «— Silicification of Diabase and Origin of 



Jasperoids - - - . . 335 

 b — Production and Alteration of 



(/orunduni ..... 337 



c — Nature and Origin of " Selwynite " - 338 



