302 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [March 8, 



sufficiently deep, the subjacent granite, or the stratified rocks on 

 which it rests. On the surface, this lava has generally a spherical 

 concretionary structure, breaking up into rounded or subangular 

 blocks ; this structure becomes columnar whenever the lava attains a 

 considerable thickness, say 100 to 200 feet ; this being probably due 

 to the slower cooling and more perfect crystallization of the lower 

 portions of the mass. A good example of this may be seen at the 

 junction of the Campaspe and Piper's Creek, where the lava and 

 subjacent stratified rocks are exposed in almost vertical cliffs from 

 200 to 300 feet in height. 



Auriferous Drift. — This formation, of very late tertiary date, 

 varies in thickness from a few inches to 100 feet and upwards, and 

 consists of stratified and unstratified masses of ferruginous clays, 

 sands, and gravel, interspersed with angular and partially rounded 

 fragments of clay-slate, sandstone, quartz, &c. It occurs almost 

 universally distributed in the gullies, on the flats, and over the hills 

 occupied by the palseozoic strata, and is in fact formed from the de- 

 composition, breaking up, and spreading out of the immediately sub- 

 jacent rocks ; the fragments found in it being, vdth a few local 

 exceptions, seldom much water-worn, and bearing no evidence of 

 having been transported from a distance. The lowest stratum or 

 bottom almost always varies in colour and character with the nature 

 of the subjacent rock, whether a ferruginous clayey sandstone, forming 

 a red or mottled ferruginous sandy clay, or a soft felspathic slate, 

 producing a white pipe-clay, &c. 



"With respect to the origin and present position of the gold, there 

 can, I think, be little doubt that the whole of it has been formed 

 in the quartz-veins which are now seen traversing the palaeozoic 

 strata ; and that its present position in the drift is entirely due to the 

 decomposition, breaking up, and spreading abroad of the quartz-veins, 

 along wdth the ordinary sandstones, slates, &c. of the district. Its 

 general position in the lowest portion of the drift, resting immediately 

 on the solid rock, is due, 1 st, to its great specific gravity, as compared 

 with the rest of the materials forming the associated drifts. 2nd. It 

 has always been supposed that gold-veins are richest near the surface, 

 and, unhke other mineral veins, gradually become poorer the deeper 

 they are followed. Such being the case, it follows that the deposits 

 now occupying the lowest portions of the Drift, formed from those 

 portions of the auriferous quartz-veins which were first broken up and 

 distributed during the period of the Drift, would be much richer 

 than any deposits formed by subsequent denudation from less super- 

 ficial portions of the auriferous veins, and all experience tends to 

 prove that such is actually the case. 



With respect to the range and extent of this Drift-formation, I can 

 only state, that every part of the country I have seen which is occu- 

 pied by palaeozoic strata (coloured lilac on the Map) is more or less 

 covered with drift of the same character, derived from rocks abun- 

 dantly intersected by quartz-veins. The real value of it can, however, 

 only be ascertained by actual working. 



Between the western boundarv of the granite and the River 



