606 HYDEAULIC MINING. 



sucli excavations may interfere materially witli the course of sub- 

 terranean waters, and it has even been conjectured that the re- 

 moval of large bodies of metallic ore from their original deposits 

 might, at least locally, aSect in a sensible degree the magnetic 

 and electrical condition of the earth's crust.* 



HydrauliG Mmmg. 



What is called hydraulic mining — a system substantially identi- 

 cal with that described in an interesting way by Pliny the elder, 

 in Book XXXY. of his ISTatural History, as practiced in his time 

 in the gold mines of Spain f — is producing important geographi- 

 cal effects in Cahfornia. Artificially directed currents of water 

 have been long employed for washing down and removing masses 

 of earth, but in the Cahfornian mining the process is resorted to 

 on a vastly greater scale than in any other modern engineering 

 operations, and with results proportioned to the means. Brooks 

 of considerable volume are diverted from their natural channela 

 and conducted to great distances in canals or wooden aqueducts,;}: 

 and then directed against hills and large level surfaces of ground 



* The exhaustion of the more accessible deposits of coal and other minerals 

 has compelled the miners in Belgium, England and other countries, to carry 

 their operations to great depths below the surface. At the colliery Des Vivi- 

 ers, at Cilly near Charleroi, in Belgium, coal is worked at the depth of 2,820 

 feet, and one pit has been sunk to the depth of 3,411 feet. It is supposed that 

 the internal heat of the earth wiU render mining impossible below 4,000 feet. 

 At Clifford Amalgamated Mines, in Cornwall, the temperature at 1,590 feet 

 stood at 100°, but after the shaft had remained a year open it fell to 83°. In 

 another Cornish mine men work at from 110° to 120°, but only twenty 

 minutes at a time, and with cold water thrown frequently over them. — The 

 Last Thirty Tears in Mining Districts, p. 95. 



Stoppani mentions an abandoned mine at Huttenberg, in Bohemia, of the 

 depth of 3,775 feet. — Corso di Oeologia, i., p. 258. 



f I have little doubt that the hydraulic mining in Gaul, alluded to by Dio- 

 dorus Siculus, Bibliotheca Historica, v. 27, as merely a mode of utilizing the 

 effects of water flowing in its natural channels, was reaUy the artificial method 

 described by Pliny. 



Xln 1867 there were 6,000 miles (including branches) of artificial water- 

 courses employed for mining purposes in California. The flumes of these 

 canals are often of sheet-iron, and in some places are carried considerable dis- 

 tances at a height of 250 feet above the ground. — Raymond, Mineral Statistiet 

 west of the Eocky Mountains, 1870, p. 476. 



