148 RATIONAL CONSTRUCTION OF FURNACES descend toward the low end of the tunnel, imparting their heat to the incoming briquets, and acted upon by the draft from the chimney, since the resistance offered by the tunnel, which has been increased in size, is not very large. The author believes that a tunnel kiln corrected as he has indicated will work in a satisfactory manner. M (1) While the author was writing these lines he did not know that, in Sweden, the principle of the tunnel kiln built on the arc of a vertical circle, had been applied with considerable success in the Aminoff furnace (Fig. 128) for the continuous carbonization of wood (Revue de la Societe russe de Metallurgie, No. 1, pp. 48-64,1912; extract, Revue de Metallurgie, decembre, 1913, pp. 678-9). These results completely confirm the author's view.