Milling improvements during the 1860s set the stage for WWI copper ...
The old stamp mill at the Phoenix Mine drove eight gravity stamps, but was increased to 24 in 1855, operated by water power. Around 1859, the company abandoned this underpowered mill, introduced a steam engine, and erected a new mill containing 48 stamps. ... "Three Ball's stamps at the Pewabic mill, Lake Superior, running from Jan. 1 to ...