400 Geological Society : — 



enough to make the right picture of the sUde coincide with the left 

 picture at the focus of the semi-lenses. The whole arrangement 

 may be easily understood ; we have only to suppose that we look 

 through a ground glass placed before an ordinary stereoscope at the 

 distance of the focus of its semi-lenses, the slide being strongly 

 lighted, and the eye seeing no other light than that of the pictiu-e on 

 the ground glass. The whole being nothing more than a camera 

 having had its lens cut in two parts, and the two halves sufficiently 

 separated to produce at the focus the coincidence of the two opposite 

 sides of the stereoscopic slide placed before the camera. 



GEOLOGICAL SOCIETY. 



[Continued from p. 326.] 



March 10, 1858. — Prof. Phillips, President, in the Chair. 



l"he following communications were read : — 



1 . "On the Geology of the Gold-fields of Victoria." By A. R. C. 

 Selwyn, Esq., Geologist to the Colony of Victoria. 



The author stated, that in the Colony of Victoria, from a line east 

 of Melbourne to some distance west of that place, he has traced a 

 .succession of fossiliferous palaeozoic rocks, commencing with schists, 

 much cleaved and contorted, and containing -Lw?y?//£e and Graptolites, 

 l)assing through a series of schists and sandstones with Trilohites 

 and many other fossils characteristic of the lower, middle, and upper 

 Silurian Series of Britain, and terminating with Devonian and Car- 

 boniferous rocks ; and he remarks that the younger or Oolitic (i) 

 coal-bearing beds on the west rest unconformably on the palaeozoic 

 rocks. A list of about sixty genera of Silurian fossils, including 

 many new species, was appended. 



The gold-bearing quartz-veins of the Silurian rocks appear to the 

 author 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. Quartz-veins do not apjjear to traverse the Oolitic (.'') coal- 

 rocks, which are of newer date than the granites of this district. 



The author's observations refer chiefly to Bendigo, Ballaarat, and 

 Steiglitz gold-fields, where Grajjtolites and Lingulce occur in the 

 schists, which are traversed by the gold-quartz veins. The granites 

 here do not contain gold ; and, though they have altered the slate- 

 rocks at the line of junction, yet they do not appear to have affected 

 their general strike or di]), but appear to have themselves partaken 

 of the movements which have placed these Silurian rocks on their 

 present highly inclined and contorted positions, and given them 

 their very uniform meridional direction. 



Mr. Selwyn recognizes gold-bearing drifts of three distinct ages. 

 The lowest contains large quantities of wood, seed-vessels, &c., at 

 various depths, to 280 feet, and is associated with clays, sands, and 

 pebbles. These are overlaid by sheets of lava. A more recent auri- 

 ferous drift, containing also bones of both extinct and living marsu- 

 pial quadrupeds, overlies these lavas in some places ; in others it 



