Victoria as a Field for Geologists, 19 



section before you. A similar ciittiiig off of the crown of a 

 hill is shown at Moonee Ponds, at Aitkin's Gap, and in 

 numerous parts of the colony. Picture, then, this same 

 district in its pristine state and elevated as dry land. We 

 shall have a scene remarkable for its picturesqueness. 

 Broken up by hill and dale, the mountain tops attracting the 

 cloud and courting the shower ; dov/n the sides of the 

 steeper precipices would roar the torrent, and along the 

 valleys would flovv^ the stream ; the whole having a climate 

 strangely different from that of Austradia now. Partially 

 sink the area, and there v^^ould appear an archipelago of 

 islands, with winding channels, deep bays, and romantic 

 fiords, bounded by rocky shores slowly crumbling away. 

 Submerged still further, and Yicfcoria T\all be an ocean bottom 

 of varjdng depth, generating currents, and forming the 

 habitat of strange denizens of the waters, as these preferred 

 homes upon the fop.m-washed rocks, or in the deeper sea. 



This, the Silurian, foi^mation is of great practical interest, 

 from the fact that it is the original matrix of the quartz 

 reefs whence, all our auriferous treasures are derived. 



First of all, then, a question of gi^eat moment presents 

 itself Do the reefs referred to, or do they not, decrease in 

 productiveness as they descend ? Not a little has been said 

 upon the subject, and not a httle bad temper towards geologists 

 has been displayed. It is a problem the practical importance 

 of which I can indicate to you, even whilst no attempt is 

 made to afford an answer. In cases where I have put pointed 

 queries upon the subject, the replies received have been 

 various and coniiicting. One thing, however, I often 

 noticed. Those having shares to sell were much more en- 

 thusiastic anti-Murchisonians than those who wished to 

 purchase. 



But there is another question quite worthy of the geologists 

 attention, namely, the probable origin of the quartz veins 

 themselves, and how the same first came to be impregnated 

 with the precious metal. 



Before you is a quarter sheet of the Government Geological 

 Map, showing the district near Castlemaine. The purple 

 tinted portions indicate the development of the Silurian 

 strata. Over these parts are scattered a vast number of 

 black lines, looking, as they are drawn, not unlike the flights 

 of arrows in some ancient battle piece. These are quartz 

 reefs. They have nearly all a meridional direction, a feature 

 in reefs by no means peculip.r to this district alone.- 

 ^ c 2 



