TEKEA-COTTA, BRICK, ETC.
125
liable to slip before the kuives, but is cut through and
through, and thoroughly mixed ; so that 1 >y the time it reaches
the small end of the temperiiig case it is ready to be formed
into bricks.
On the end of the tempering sliaft is secured a conical
screw, which revolves in a cast-iron conical case, the inside
of which is pitted, checked, or ribbed, so as to prevent the
clay frorn revolving in it, and is chilled, to prevent wearing.
The screw being smooth and very hard, the clay slides on
it, thus becoming, as it were, a nut; the screw revolving, and
the clay thus not being allowed to move backward, it must go
forward.
This Operation further tempers the clay, and delivers it, in
a solid, round column, to the forming die, which is of peculiar
coustruction and form, and so designed as to reduce the round
column to a rectangular one, whose breadth and thickness is
the proper breadth and thickness for a blick, wliile at the sume
time the clay isforced into the corners of the finishing part of
the die, so that the angles of the bar of clay are made full,
solid and sharp. This column of moulded clay, as it issues
frorn the die, is conducted by an endless beit, supported on
rollers, to the cutting device, which consists of a thin blade
of steel, secured to the periphery of a wlieel, passiug through
the bar of clay, and being guided by steel plates, so arranged
as to move with the clay while the knife is passing through it,
and so as to Support the under-side and edge of the bar while
being cut.
The bricks are tlien dusted with fine sand, and are conveyed
on cars or barrows to the packing-floors or drying-chambers.
One of these machines will make frorn twenty-five thousand
to thirty-five thousand bricks regularly, in ordinary clays,
per day of ten hours; or frorn fifty to eighty bricks per
miniitc.
Messrs. Chambers & Brother made some experimeuts to
determiue the crushing pressure of bricks made by this ma-
chine out of New Jersey and Bhiladelphia clays, with the fol-
lowing results:—
