Selwyn — On Quartz-Reefs and Gold-Drifts. 459 



witliout the interventioii of the marine beds or of the older basalt, 

 both so well shown lower down the same valley. 

 The section near the Golden Elvers is : — 



1. Upper basalt-rock, about 25 to 30 feet. 



2. Pliocene gravel, about 50 to 60 feet. 



3. Miocene gravel, etc. ("false bottom of miners"), gravel, sand, 



clay, and boulders, with fossil-leaves and wood ; about 400 feet, 



4. Silurian slates, etc. 



The section on the Moorabool, west of Steiglitz, is : — 



1. Basalt, upper, 49 feet. 



2. Sandy Pliocene grit, 10 to 15 feet. 



3. Upper coralline limestone (Miocene), 13 feet. 



4. Older basalt, enclosing bands of hard compact limestone with 



fossils (Miocene). 



5. Sandy limestone, with fossils, 30 feet (Miocene). 



6. Bounded quartz pebble-drift, and hard silicious conglomerate 



rock, with fossil wood, lower part a gravel and boulder drift, 

 90 feet. 



7. Silurian slate and sandstone with quartz veins. 



No. 6 of this section represents No. 3 of the Golden Elvers, 3, 4, 

 and 5 being absent in the latter. The thicknesses given are only 

 approximate, and of course vary in different sections. 



In support of the theory I have advanced respecting the non-auri- 

 ferous character of a set of what I believe to be the older quartz - 

 veins, and from which the Miocene gravels have, probably, in great 

 part, been derived, I would mention a fact well known to all ex- 

 perienced quartz -miners, viz., that in many districts numerous large 

 lines of reef occur that are entirely barren, though in close proximity 

 to others affording handsome returns. These reefs present no pe- 

 culiar features either in external character, general appearance, or 

 mode of occurrence, that would enable an ordinary observer, unac- 

 quainted with the reefs of the district, to distinguish them. They 

 are, however, I believe, recognised without much difficulty by the 

 practical quartz -miner. 



Now unless there really is, as I suggest, some marked difference 

 in the time, and also in the conditions under which these different 

 reefs were formed, it is difficult to explain why one reef should be 

 richly auriferous, while another, in close proximity, is entirely barren, 

 if formed at the same time and under similar conditions. In attempt- 

 ing to reconcile these facts, I have arrived at the conclusion, that 

 there must be two, if not more, distinct sets of quartz veins — that 

 the older ones were formed prior to the Miocene period, and are 

 barren ; and that the newer ones AVere formed after the close of the 

 Miocene epoch, and before the Pliocene, and are productive. The 

 former have furnished the material for the barren Miocene gravels ; 

 and the latter have furnished the material for the productive Pliocene 

 gravels. 



Victoria, May iili, 1866. 



