ORES OF GOLD 55 
A deep lead must be 100 feet deep according to Victorian law, 
or over 20 feet deep by that of Western Australia. The rich- 
ness of the drifts at Golden Point was due to the river having 
cut through the indicator belt of Ballarat East (cf. p. 40) 
and to the repeated rewashing of the gravel as the valley 
was deepened and enlarged. The leads on the western slopes 
of Ballarat East disappeared at the foot of the plateau of 
Igneous rock which was called ‘hypogean trap; as it 
was regarded as deep-seated, there appeared no chance of 
the leads passing beneath it. This wall of rock blocked pro- 
8ress, so the miners named it Sebastopol—the Crimea war 
being then in progress. Meanwhile in the neighbouring 
Fie. 17.~A Hicu Lever Deep Leap. 
A dissected high level Deep Lead. A modern river, AA, has cut its valley 
between two hills—contours at 200 and 300 ft. A Deep Lead flow- 
ing from 1go ft. at the eastern end to 170 ft. at the west has been cut 
through by the modern river, and rich gravels occurred at XX where 
the gold from the old river gravel had been redeposited. 
field of Creswick it was found that a lead continued under a 
similar igneous rock, which was therefore a sheet of lava and 
not a deep-seated mass. i 
This success led the Ballarat miners to renew their siege 
of the Sebastopol plateau; they mined underneath it and 
found that the leads from Ballarat East continued west- 
ward under five lava flows, and joined the main lead of the 
river that drained the area before the volcanic eruptions. 
The working of this lead was impossible while alluvial miners 
were allowed claims of only 20 feet square. By successive 
concessions the mines were enlarged to prospecting areas of 
1000 acres and ultimately leases of 5000 acres. This en- 
largement of the claims rendered possible boring across the