1858.] selwyn victoria. 533 



March 10, 1858. 



Alfred Williams, Esq., C.E., Newport, was elected a Fellow ; A. 

 Escher von der Linth, Zurich, and E. Deslongchamps, Caen, were 

 elected Foreign Members. 



The following communications were read : — 



1 . On the Geology of the Gold-fields of Victoria. By Alfred 

 R. C. Selwyn, Esq., Geologist to the Colony of Victoria. (In a 

 Letter* to Professor A. C. Ramsay, F.R.S. and F.G.S.) 



I have now a very large collection of genera and species of Silurian 

 fossils, many of them known forms, and many new. M'Coy is 

 going to examine, describe, and figure the new ones. I shall, I hope, 

 soon be able to define the boundaries of the Upper and Lower 

 Silurian rocks in this colony. Melbourne stands on " May Hill 

 Sandstone ;" and to the eastward I find a very gradually-ascending 

 series, including probably Wenlock, Ludlow, Devonian, and true 

 Carboniferous rocks, with Oolitic coal-bearing beds resting uncon- 

 formably on the Palaeozoic strata. To the westward there is a 

 descending series, from Melbourne towards Ballarat, which I much 

 suspect to be Cambrian. 



Lingulce, like those of Tremadoc, are abundant in the rock asso- 

 ciated with the Bendigo gold-quartz mines. In beds which I take 

 to be equivalents of the Llandeilo flags, Trilobites are very abundant 

 — many of them recognizable European species. I enclose a list of 

 genera (p. 537). This list is now, however, much increased, and is 

 being added to daily. 



Gold-bearing quartz- veins extend throughout the Silurian rocks; 

 and their richness appears to me to be dependent more on their 

 proximity to some granitic or other plutonic mass than on the age 

 of the rocks in which they occur. As far as I am aware, these gold- 

 quartz veins do not extend into the Oolitic (?) coal-bearing rocks, 

 which are evidently of newer date than any of the granitic masses 

 I have yet examined. 



At Steiglitz (fig. 1), we have granite (a) intruded among Silurian 

 sandstone, conglomerate, slate, &c. (b), which are cleaved and inter- 

 sected by veins of auriferous quartz (c), and contain Graptolites, 

 Lingulce, &c, and perhaps represent both Upper and Lower Silurian 

 strata. The granites here never contain gold or quartz-veins. Similar 

 auriferous quartz-veins traverse the Lower Silurian cleaved sandstones 

 and slates at Bendigo and Ballarat, as shown in figs. 2 and 3. These 

 strata also contain Graptolites, Lingulce, and other fossils. 



One somewhat remarkable point, in connexion with nearly all the 

 great granitic masses that I have examined, is that, though they 

 invariably alter the slate-rocks near their junction, and send veins 

 into them, they do not in the slightest degree affect the general 

 strike or dip of the latter, but appear to have themselves partaken 



* Dated 10th September 1857. 



