ON THE AUSTRALIAN GOLD FIELDS. 117 



host of smaller gold-bearing localities may be described 

 almost in the same terms — as valleys or gullies among 

 low schistose hills. But not uncommonly the auriferous 

 drift assumes so level an upper surface as to be denomi- 

 nated a flat. 



Ballaarat. • — I come now to the celebrated Ballaarat, 

 the great richness and still more the complicated and 

 remarkable structure of which render it by far the most 

 interesting of the Australian gold fields. We shall be 

 greatly assisted, too, in understanding its geological forma- 

 tion by the excellent geological map produced under the 

 direction of Mr. Selwyn, government geologist of Victoria. 



From this map it will be seen that Ballaarat consists 

 of a somewhat basin-shaped accumulation of alluvium, or 

 auriferous drift, surrounded by detached and bold hills of 

 schistose or slaty rock, between which run various gullies 

 filled by extensions of the alluvium. All the inequalities 

 of the surface and the continuity of the depressions may 

 be clearly traced by the contour lines. A very large part 

 of the total area of alluvium is distinctly auriferous, and a 

 large part indeed has been turned up or undermined by 

 the gold diggers in their eager search. But on the map 

 only those spots of ground are marked as gold workings 

 where the deposit was especially rich ; now it has been 

 found and is shown that these richest deposits occur in 

 broad continuous lines or bands called leads of gold, which 

 occupy the deepest depressions of the schistose bottom 

 rock. The leads are all branches of one main lead or body ; 

 and while the elevation of the bottom of this main lead is 

 about one thousand two hundred feet above the sea, the 

 branch leads universally show a more or less gradual rise 

 of level. It may be observed, too, that the leads show 

 scarcely any coincidence with the present gullies or water- 

 courses, and do not bear a very distinct relation even to 

 the position of the present schistose hills. 



