fire brick, which joins the fire-brick lining of the interior of the
shaft, this latter being bonded to the red-brick walls to a point 6
feet below the top of the octagon, and extended above for a height of
14 feet within the circular shaft, as an inner shell. The usual baffle
wall is provided of fire brick, 13 inches thick, extending diagonally
across the chimney, and 4 feet above the tops of the flue openings.

Where the chimney passes through the roof of the boiler house, a steel
plate and angle curb, which clears the chimney by 6 inches at all
points, is provided in connection with the roof framing. This is
covered by a hood flashed into the brickwork, so that the roof has no
connection with or bearing upon the chimney.

At a point 4 feet 6 inches below the cap of the chimney the brickwork
is corbeled out for several courses, forming a ledge, around the
outside of which is placed a wrought-iron railing, thus forming a
walkway around the circumference of the chimney top. The cap is of
cast iron, surmounted by eight 3 x 1-inch wrought-iron ribs, bent over
the outlet and with pointed ends gathered together at the center. The
lightning conductors are carried down the outside of the shaft to the
roof and thence to the ground outside of the building. Galvanized iron
ladder rungs were built in the brickwork, for ladders both inside and
outside the shaft.

The chimneys, except for the octagonal red-brick base, are constructed
of the radial perforated bricks. The lightning rods are tipped with
pointed platinum points about 18 inches long.

[Sidenote: _North River
Pier_]