Apparatus for the primary distillation of shale or other bituminous minerals in large quantity is constructed as follows:--An annular retort chamber is heated by two or more furnaces, one of which communicates with a central or internal vertical flue, and the others with external or encircling flues preferably disposed in zig-zag, helical or other tortuous course; or the gases pass up the external flues and down the internal flue or flues. The retort chamber may be divided by partitions, or there may be two or more separate chambers disposed concentrically or otherwise with intermediate flues. A pipe or pipes are provided to carry away volatile matters, and valved hoppers are arranged at the top of the retort chamber. The refuse or waste passes off by discharge tubes between the furnaces, and the mouths of these tubes dip into water tanks. The bottom of the retort chamber is funnel-shaped at the discharging points. The apparatus is preferably cylindrical, but may be triangular, square, or polygonal, and may be inclined or horizontal instead of vertical.