The object of the invention is to treat the coal residues, shale, and other bituminous material in a way to extract as large a portion as possible of the tar and oil and, consequently, it is proposed to work at temperatures of 300 to 500/sup 0/C, the apparatus being arranged in a way to realize as completely as possible the conditions of treatment. On a foundation, a cylindrical retort is arranged horizontally, made of cast iron, fire clay, or other convenient material, the dimensions and form of which may vary. In the same way, two other retorts of the same length but smaller in diameter are arranged above the first. They are horizontal and a little distance from each other. They carry at one end a charging hopper and at the other pipes which lead into the larger retort.