306 ON THE TRANSMUTATION OF ROCKS, &c., 



The only difference which I think may occur in rocks, trans- 

 muted by basalt and granite or greenstone, is the presence in the 

 latter of an alkali derived from the greater proportion of felspar in 

 the transmuting agent. Both Mr. Miller and Mr. Ulrich of the 

 Victorian Geological Survey undertook for me the delicate 

 analysis of the Cooper's Creek and Sappa Bulgas rock for alkali, 

 and a minute proportion was detected by each of them. 



I do not know whether any alkali has been traced in these 

 transmuted sandstones near Sydney. I am myself unable to 

 determine it. 



Certainly, we have no such complete vitrifications near 

 Sydney as at Green Ponds, in Tasmania ; but, on the other hand, 

 though I found imperfect prisms near Lovely Banks, in the same 

 district, in contact with trap, I have never seen such perfect 

 columns as those we can find in this neighbourhood. Tasmania 

 may yet produce them ; but I did not see any in the course of a 

 very careful survey of the valley of the Jordan, and at Jericho, 

 where contacts are common. 



There are, however, other changes produced on the south of 

 Green Ponds (near Bagdad, and about Constitution Hill) on beds 

 of the Carboniferous formation which are worthy of notice. These 

 portions of shale, containing casts of plants, are filled with 

 chalcedonic veins. I broke them from masses in contact with 

 the igneous rock now exhibited. 



The facts which I have now endeavoured to illustrate are, 

 that there is an intimate relationship between prismatised rock, 

 ferruginous deposits, silicate of alumina, and basaltic and trappean 

 outbursts. This will be further strengthened if we consider that 

 silicate of alumina abounds in certain trappean rocks ; and 

 that various clays are constantly found in association with 

 them. 



1 have also endeavoured to point out not only the probable 

 connection of the physical features of our own vicinity with the 

 causes of igneous action beneath us, but that there is proof 

 abundant to show that the solid rocks, whether sedimentary or 

 intrusive, are still undergoing constant change, and that no part 



