I-beams. The grillage is filled solidly with concrete and flushed
smooth on top to receive the brickwork of the chimney.

Each chimney is 162 feet in total height of brickwork above the top of
the supporting platform, and each chimney is 23 feet square in the
outside dimension at the base, changing to an octagonal form at a
point 14 feet 3 inches above the base. This octagonal form is carried
to a height of 32 feet 6 inches above the base, at which point the
circular section of radial brick begins.

The octagonal base of the chimney is of hard-burned red brick three
feet in thickness between the side of the octagon and the interior
circular section. The brick work is started from the top of the
grillage platform with a steel channel curb, three feet in depth,
through which two lines of steel rods are run in each direction, thus
binding together the first three feet of brickwork, and designed to
prevent any flaking at the outside. At a level of three feet above the
bottom of the brickwork, a layer of water-proofing is placed over the
interior area and covered with two courses of brick, upon which are
built diagonal brick walls, 4 inches thick, 12 inches apart, and about
18 inches in height. These walls are themselves perforated at
intervals, and the whole is covered with hand-burned terra-cotta
blocks, thus forming a cellular air space, which communicates with the
exterior air and serves as an insulation against heat for the
steelwork beneath. A single layer of firebrick completes the flooring
of the interior area, which is also flush with the bottom of the flue
openings.

There are two flue openings, diametrically opposite, and 6 feet wide
by 17 feet high to the crown of the arched top. They are lined with