The distillation and rectification of tar, resin, bitumen, turpentine, shistore oil, and other substances, have been improved by M. D'Arcet, with a view to obtain a continuity of action. The principal object of the invention, and of the apparatus employed to carry it into effect, is to render the distillation of the above-named substances, and generally of all liquid hydro-carbons, liquifiable by heat, analogous to that of alcoholic liquids, and to effect this purpose at the lowest'possi-ble degree of temperature. The basis of the process may be said to consist in the continuity of the distillation or rectification, and the spontaneous separation of the resulting volatile substances. For this purpose they are placed in an apparatus divided into compartments, to each of which, in succession, increased degrees of temperature are applied. Each compartment is provided with an escapement valve, by which the products of distillation in that degree of temperature are conducted into a separate receiver.