... [The Smelter.] The furnace or smelting apparatus consisted of a round hollow in clayey gound, thirty centimeters in diameter and fifteen deep; with which was connected a conical funnel of fire-proof stone, inclined at an angle of 30 deg., carrying up two bamboo-canes, which were ... — The Former Philippines thru Foreign Eyes • Fedor Jagor; Tomas de Comyn; Chas. Wilkes; Rudolf Virchow.