“ Alternate layers of pots and tan-bark are filled up to the roof of the chamber: air is introduced into the chamber through flues and natural crevices. The tan contains moisture, becomes heated, and evolves carbonic acid. By chemical action the lead is oxidized by the oxygen of the air, and then, in combination with the carbonic acid, becomes a carbonate of the oxide of lead. ”

“ Orange or red lead is made by roasting dry white lead in a furnace, and exposing it to the air which is admitted into the heated receptacle. By this process the white lead loses a portion of its carbonic acid, and absorbs oxygen from the air. Orange or red lead is used by paper-stainers, manufacturers of wall-paper, and for highly-colored cards. ”

“ Sheets of zinc ordinarily sold in commerce are placed in retorts. The face of the retort has an opening large enough to admit the sheet. The backs of the retorts are enclosed in a furnace, and the retorts are heated by bituminous coal to a white heat. The action of the heat vaporizes the spelter, which is entirely consumed. ”