288 Proceedlvjj.s of the Royal Society of Victoria. 



the ridges below l)otli the Caledonian and Devonshire Reefs was 

 carefully panned from a great many places, but not a particle of 

 such crystalline gold as characterises both tlie pebbles and the 

 bed-rock in the lead could be discovered. 



It is necessary here to understand the physical conditions 

 existing in the locality. The Caledonian Lead represents an old 

 watercourse that ilowed along the bottom of a valley, which has 

 since become filled up with alluvial matter to a depth of 90 to 

 135 feet above the old water course, and this alluvial ground is, 

 at the surface, from 10 to 30 chains aci'oss. North and south of 

 the valley are spurs of Ordovician rock, and the floor of the 

 valley is the same rock. Cutting through these rocks in a 

 north-westerly direction and crossing through the valley from 

 side to side are the Caledonian and Devonshire Reefs. On each 

 side of the valley the spurs rise for from 100 to 200 feet above 

 the present surface of the alluvial flat. 



Rain falling on the spurs percolates through the sandstones 

 and slates, dissolving alkalies and other matters, and finds its 

 freest channel along the course of quartz-lodes, such as the 

 Caledonian and Devonshire, and this water, after traversing 

 such auriferous lodes through a depth of 200 or 300 feet, is 

 discharged into the lead drainage where the reefs are crossed. 

 During its passage through the gold-bearing quartz and accom- 

 panying sulphides it dissolved some of the gold, and where it flows 

 into the lead re-deposited the gold in the porous sandstone pebbles 

 and in the rocks forming the floor of the lead, where the conditions 

 were favourable. 



The Caledonian Lead is practically dry in the sunnner season, 

 as the Indigo Lead drains the water away from it ; but in the 

 winter the rains ppi'colate through the rocks and through the 

 alluvium, and then water flows down its course, percolating 

 through the pebbles, etc., and in this manner depositing gold. 

 Doubtless the water contained but a very small amount of gold, 

 and the process of deposition in the pebbles and bed-rock was a 

 very slow one. Very probably it was also a process continued to 

 the time the lead was worked, and even may now be active. 



Auriferous pebbles also occur in other localities on this Held. 

 The writer obtained examples on the Indigo Lead, above its 

 junction with Wallace's Gully Lead, and also in the last but one 

 north branch on the west side of Wallace's Gully Lead. 



