78 FACTS IN AMERICAN MINING. 



The Comstock lode lies at the junction of syenite and propylite, 

 occupying the contact plane, along the entire front of the Davidson 

 Kange ; in places north and south it is entirely walled by propylite ; 

 this rock is a species of greenstone, beiog composed of oligoelase 

 and hornblende. 



Methods or Gold-mining. 



Hydraulic mining is in great favour in California, but in New 

 South Wales its existence is hardly known. Immense works are 

 undertaken by the enterprising Americans for carrying on this 

 method of mining on a large scale, and hundreds of thousands of 

 pounds have been expended in bringing large bodies of water from 

 distances of 30 or 40 miles for the purpose of washing away whole 

 hills to get at the ancient river beds below containing the gold. In 

 the Blue Gravel Company's claim a tunnel of 1,700 feet bad to be 

 cut to ascertain if the ground was payable, in some cases costing 

 £20 per loot. After five years of hard labour the Company had 

 spent £20,000 and were still without any certainty of finding gold. 



They now use 500 inches (miners' measurement) of water, 

 equal to a stream of 3 feet wide and 8 inches deep, running at 

 high velocity. They consume over 60 tons of powder annually in 

 loosening the ground, and 3 tons of quicksilver at a time to 

 catch the gold. This Company pays £ L5 per day, or about £5,000 

 a year, for the water supplied to them. 



To give some idea of the magnitude of the waterworks, I may 

 here mention that the Eureka Company constructed 250 miles of 

 race, at a cost of over £180,000. This Company's receipts for 

 water used, at one time, to be a thousand pounds per day. In 

 1867 there w r ere no less than 6,000 miles of canals or races in the 

 Western States. 



A very ingenious device for carrying w r ater long distances 

 and avoiding circuitous detours in hilly country has been adopted 

 by the introduction of inverted syphons, for carrying water up the 

 sides of bills, by the heavier pressure of a column brought down 

 the opposite slope. 



Sluices of great magnitude have been constructed for gold- 

 washing, and in cases where the gold is fine they have been con- 

 structed over a mile long ; and ground sluices where large bodies 

 of washdirt had to be treated by rapid and inexpensive processes. 

 Few persons unacquainted with this description of gold-mining 

 have much idea of the small quantity of gold that may be made 

 to pay in ground sluicing, with a good head of water. At a small 

 claim on the Shoalhaven, in this country, a cubic yard of earth 

 containing six pennyworth of gold pays wages, and leaves a profit 

 for dividends ; and in this particular claim I have washed out 

 payable gold below the tail race, a mile from the spot it was 

 washed from, 



