Measures to secure a patent for the above have been taken by Elisha K. Root, of Hart ford, Conn. The nature of this invention consists in the peculiar construction and ar rangement of the cold air passage and flue of the lurnace, whereby the cold air is made to pass over a great area of heated surface and ! a large volume of heated air is obtained with a small quantity of fuel. For this purpose the cold air passage is so arranged that the air is heated by passing around the smoke-pipe, as well as by being brought into close proxi mity with the hot air flue, and is after wards brought into contact with a dome Which is placed over the fire-chamber and communicates with the hot air flue. It has now become completely heated, and is con veyed through the proper tubes or pipes to those apartments or portions of the building designed to be heated. The other improve ments consist in the arrangement of the ash pit and in an inclined passage leading upward to the fire-chamber for supplying it with fuel, the object being to prevent, by this contri vance, any escape of gas from the fire-cham ber otherwise than by the hot-air flue.