Clarke — On Australian Gold-Reefs. 561 



The data from which have been inferred the relative ages of the 

 two great movements of disturbance that gave rise to the contortions 

 and many of the minor faults of the rocks of North Wales are lucidly 

 explained. But we can do no more than merely direct attention to 

 these and the many other important questions that come up for dis- 

 cussion in the memoir. No one can only glance over its pages and 

 their numerous illustrations without being impressed with the 

 abundant proofs of tremendous denudation which every mountain 

 and valley of the region exhibits. The former extension of certain 

 beds is indicated upon plate xxviii, from which it may be seen that in 

 some places a thickness of solid rock has been removed to the amount 

 of 20,000 feet, and this does not take account of the still higher beds 

 which are believed to have originally swept over the now denuded 

 strata. The mind is lost in trying to apprehend the time requisite 

 for the gradual transport of such immense masses of strata. And if 

 we believe, with Prof. Eamsay, that the valleys have been cut out in 

 old table-lands (plains of marine denudation), "by the weather, by 

 running water, and by glaciers ; " that, in short, the old mountains 

 of Wales have grown into existence no faster than hills of denudation 

 are forming now, to what an inconceivable distance in the past does 

 the beginning of all these slow changes appear to recede. 



The bulky Appendix is devoted to lists and descriptions of the 

 fossils illustrative of the memoirs, for which we are indebted to Mr. 

 Salter, whose ability as a palseontologist, and whose intimate acquaint- 

 ance with palceozoic forms, are sufficient guarantee for the value of 

 this portion of the work. Of the 26 plates of fossils that accompany 

 the Appendix it is enough to say that they have been prepared by 

 Messrs. C. E. Bone and W. H. Baily. 



II. — ^Eev. W. B. Clarke on the Atibiferous and Non-Aueifekous 

 Quaktz-Eeefs of Australia. 



SINCE the publication of Mr. Selwyn's report on the Auriferous 

 Drifts and Quartz-Eeefs of Victoria, (p. 457,) our attention has 

 been directed to a recent number of the ' Sydney Morning Herald,' 

 (June 8, 1866) in which Mr. E. S. Hill points out that in a paper 

 read in 1864 before the Geological Society of London, Mr. W. Keene 

 had clearly indicated the position of the division of auriferous and 

 non-auriferous rocks ; and that it is to Mr. Keene, and not to 

 Mr. Selwyn, that we are indebted for the earliest information on this 

 subject. In reference to this assertion, he quotes the following 

 passage from Mr. Keene's paper. — " I also divide the quartz as 

 belonging to different epochs. That is to say, there is a quartz at 

 the base of the Coal Measures, in many cases of great j^urity, in 

 which I have in vain sought for any sign of gold ; whilst the 

 auriferous quartz is in upheaved beds, with which the Coal Measures 

 are unconformable, and contains the old fossiliferous limestone, and 

 drift-gold is to be found where this limestone and the accompanying 



VOL. in. — NO. XXX. * 36 



