BY THE REV. J. MILNE CURRAN. 207 



masses in the granite, into the substance of which they have been 

 in process of being absorbed. The width of the belt characterized 

 by these fragments is very variable, and where the plane of the 

 present surface cuts that of the junction of the two classes of rocks 

 at an acute angle — as is often the case — it is considerable, 

 frequently exceeding half a mile. . . . The only explanation 

 which appears to satisfactorily account for the appearances met 

 with, is, that we have at the surface a plane which was at one 

 time so deeply buried in the earth's crust that the rocks beneath it 

 had become subject to granitic fusion or alteration."* 



The bearing of these extracts on the geology of Bathurst is 

 obvious. Here we have Silurian rocks resting on a granite. There 

 must have been a solid floor on which they were deposited. The 

 granite on which they rest was certainly not the pre-existing base- 

 ment. And it is extremely improbable that granitic rocks formed 

 the crust from which the sediments were derived. Thus far the 

 conditions are very similar; and it is hard to resist the conclusion 

 that when the original floor of the Silurian was being absorbed in 

 the granitic magma, some of the Silurian rocks suffered a like fate. 



The Devonian and Carboniferous formations are now estimated, by 

 Mr. C. S. Wilkinson,! to measure 20,000 feet in thickness. "With 

 two miles of strata resting on our Silurian rocks, we can see the 

 possibility of the lowest series being brought within a zone of 

 fusion, which would furnish the required magma, and make the 

 Bathurst granite, in a sense, at once metamorphic and intrusive. 



We have abundant proof, as shown above, that the granite is 

 intrusive in character. It is quite another question to decide 

 whether the material that forms the granite was drawn from a 

 deep-seated source, or whether it is the result of the profound 

 metamorphism of a previously existing sediment. 



* Annual Report of the Geological Survey of Canada, 1887 ; Report B., 

 pp. 11-13. 



t See " Notes on the Geology of New South Wales," by C. S. Wilkinson, 

 F.G.S., contained in "Mineral Products of New South Wales;" Sydney, 

 the Government Printer, 1887. 

 14 



