A thick black unctuous substance, obtained chiefly from old pines and fir trees, by burning them with a close smothering heat. It is prepared in great quantities in Norway, Sweden, Russia, Germany, North America, and in other countries where the pine and fir abound.
The mode practised in the Scandinavian peninsula, is similar to that described by Theophrastus and Dioscorides, as in use in ancient Greece. A conical cavity is made in the earth, with a cast-iron pan at the bottom, to which is connected a pipe to carry off the liquid. Billets of wood are thrown into the cavity, and being then covered with turf, are slowly burnt without flame. The tar which exudes during the combustion, is conducted by the before-mentioned pipe into barrels, which are afterwards bunged up, and are then ready for exportation.
Becher, the celebrated chemist, first proposed to make tar from pit-coal. Manufactures for this purpose have been established many years ago, in several parts of England. In the year 1781, the earl of Dundonald obtained a patent for extracting tar from pit-coal, by a new process of distillation; a kind of tar is also produced from the pit-coal used in the production of gas for illumination. See Gas: also Pitch.