XVlll PRESIDENTIAL ADDRESS. 



inches across. I generally found I could predict the coming on 

 of the granite by the alteration in the structure of the limestone. 



Here and there, as for instance at South Ruddygore the 

 the limestone is faulted and tilted, and then seems to be inter- 

 Itedded, but the true lie of the beds can always be made out by 

 .accurate mapping. 



The limestone contains a certain amount of silica and iron, 

 iind the iron has in many places been deposited as a true iron- 

 .stone at its base. This ironstone, when exposed on the surface 

 by denudation, has often been mistaken by prospectors for the 

 ferruginous gangue of the copper and silver ore. It is, of course, 

 ■quite barren. 



The obscure and scanty fossils as yet found in the limestone 

 •do not warrant us in speaking confidently of the exact 

 iige. Both Messrs. Etheridge and Jack consider the evidence 

 tells in favour of its being Carboniferous. 



I hope shortly to present a memoir on this interesting 

 formation to the Society. 



t d.j Munt((Ibi(>n Beih. — The hill which gives its name to 

 Montalbion and some of the adjacent country, is made up of a 

 series of more or less calcareous shales and sandstones, with 

 seams of clay ironstone. They are, as a rule, so little altered, 

 .and lie at such comparatively low angles, that I am inclined to 

 suspect they are distinct from, and overlie unconformably, the 

 Herberton beds. The boundary I have not had time to follow 

 ■out, but they seem to be limited to the vicinity of Montalbion, 

 .and probably only exist as outliers. 



Should this suggestion prove correct, the Montalbion beds 

 will probably prove to be of Lower Carboniferous age. 



(e.) Herberton Beila. — The enormous series of slate, shales, 

 ■conglomerates, grits, sandstones, and greywackes, which con- 

 stitute the mass of the country between Herberton and Arbouine, 

 were formerly classed with the Gympie Beds, which are of 

 Permo-Carboniferous age. Mr. Jack has since obtained evidence 

 that they are older, and must be relegated to the Devonian 

 system, a conclusion in which I agree, and which fits in well 

 with my proposed new classification. 



