The smelting and refining of the metal ores is also an important industry.
In this part of the township a copper mine was worked between 1705 and 1745, and smelting and refining works were built in 1721.
The mines once produced 3000 tons of metal annually, copper smelting being largely carried on, but have now almost ceased working.
The principal industry is the smelting and refining of lead, and the smelting works are among the most interesting sights of the city.
In Roman times, and until 1900, however, owing to lack of fuel, the smelting was done on the mainland.