A fire-proof door, designed by the writer, and in use in several large cotton and woolen mills, in one of which it has withstood an intense heat, and was the means of saving a large amount of stock and machinery, may be de scribed as follows: A plain wooden door was made of two thicknesses of seven-eighths pine, one thickness laid perpendicular, the other across. Around the edges of the door a slat of the same stuff, 3 inches wide, was nailed, the edges projecting on each * side beyond the body of the door. On these slats the sheet-iron covering was laid, thus leaving a chamber on each side the door between the iron covering and the wood. About every eight inches a common round head wood screw was put through the iron, and into the wood of the door. The edges of the iron were lapped around the edges of the door, and securely nailed thereto. Plaster of Paris mixed thin with water, in which a little glue had been dissolved, was then poured into the chamber of the door through a small aperture, and after the chambers were full and had become hard, the screws were turned down hard, binding the iron door onto the plaster. The casing of the door was treated in a similar manner, the mode of doing which will readily occur to a practical man. The cost of such a door is merely nominal, and its capacity for enduring intense heat is far beyond that of any door composed wholly of iron. This arrangement is not patented. OLD FIREMAN.