Inside the Mill.  According to Walter Dunnigan; only one man to a shift is required to oversee the operation of the mill. A Model A engine revolves the brick-and-asbestos-lined rotary kiln and only burns one gallon of gas per hour. The heating unit maintains a temperature of 1200 to 1600 degrees in the roasting drum and burns from seven to nine gallons of diesel per ton of ore in the course of 24 hours of operation.
  The roasted ore is converted to the form of a vapor and the quicksilver then passes through a series of condenser pipes and is ultimately deposited in special containers filled with water. Since the liquid mercury has a specific gravity of 13.6, it settles immediately to the bottom and the covering water effectively seals off the poisonous fumes which formally presented a grave hazard to anyone who worked around the mercury.