Poling

—1. Planks temporarily supported against the sides of excavations to prevent caving in. 2. In copper refining, an operation in which a large pole of green birch or oak is thrust down to the bottom of the furnace containing the molten copper. Violent boiling ensues, consequent on the liberation of oxygen from di olved oxides of copper. Frequent a ays are taken, and when the specimen shows by its long silky fracture that the poling proce has been sufficiently prolonged, the copper is ladled off.. In mining, a method used to support the roof of a tunnel which is being driven through unstable formation. Long narrow boards, laths, or poles, rest at a slight inclination on the top of two trestle like frames, the size of the excavation. As the work progre es, the boards are driven forward, thus keeping pace with the pick, and when projecting sufficiently far, a fresh frame is erected to support the hanging end, the proce being continually repeated.