310 Scientific Proceedings, Royal Dublin Society. 



results are few, although at other metallurgical works important 

 modifications have been introduced with very satisfactory results, 

 some of which will be noticed presently. 



At Pary's Mine, Anglesea, both a rude wet process for treating 

 the poor ores, and a treatment of the mine drainage were practised 

 over a century ago. The former seems to have been abandoned, 

 but the latter has been continued with little alteration.* The 

 waters are run through a series of large tanks containing scrap- 

 iron; in each tank the waters remain in contact with the metals for 

 some time before being drawn off to the next lowest in the series ; 

 in this manner the waters are passed from one tank to anothei, 

 and are altogether about ten weeks under treatment. At Mona 

 Mine a similar method of procedure seems to have been adopted. 



The mine waters of the Devonshire Great Consolidated Copper 

 Mines, and of Wheal Agar, near Crow's Nest, Cornwall, have also 

 been treated for the contained copper. Since 1804< pits have 

 been opened along the Great Gwennap adit, Cornwall, but the 

 results have been very low. (Table A, No. VI.) At Huel Margery, 

 St. Ives, the copper solutions have been heated by a steam jet 

 which has been found greatly to accelerate precipitation. Copper 

 is also extracted from the washings after calcination of the tin 

 ores containing pyrites.j 



On the Continent of Europe we find that copper is often ex- 

 tracted from its solutions. The following are some examples: — 



At E.io Tiato (Huelva) both the mine drainage and the poor 

 ores are treated. The one is known as " natural cementation,^' 

 the other as " artificial cementation." The ordinary method of 

 precipitation on iron seems to have been known for over 200 

 years. In the San Roque adit the launders are over 1000 yards 

 long, and contain pig-iron, which in ten days is coated with a 

 hard metallic coating of copper containing 80 per cent, of pure 

 metal. These scales are removed to expose a fresh surface of 

 iron, and are said to be so hard as to resist a file, and ring when 

 struck with a hammer. The mine drainage of Tharsis (Huelva) 

 and San Domingos (Portugal) are similarly treated.;}: 



* See T. F. Evans in Trans. Manchester Geological Society, Vol. XIV., p. 367. 



f Cementation appears to have been discontinued in Cornwall of late, as Anglesea and 

 Leinster, Ireland, are the only localities whose returns of copper precipitate appear in the 

 Mining Inspector's Eeport for 1881. 



X In " artificial cementation '' as conducted at Eio Tinto, the ore is calcined in bee-hive 

 shaped heaps or ^^teleras" containing from 100 to 500 tons. When lighted a slow com- 

 bustion continues for eight or nine months, when burnt out the ore is " removed to large 



