steam all round both the sides and bottom of the interior
vessel. The internal casting is again divided horizontally into two
partitions, one above the other therefore, by two plates, between which
also there is a space left for the admission and circulation of steam;
and a communication is kept up between the upper compartment and the
under by means of a stripping valve. Besides this, there is a
communication from the internal kettle through the external one, and
also a shaft passes between the two horizontal parts to give motion to
the stirrer, which revolves thirty-six times a minute. A cover encloses
the top, and it is through this the vessel is charged. The upper portion
is filled first, where the contents introduced are allowed to remain ten
or fifteen minutes, after which the valve is opened and the whole falls
into the lower kettle, where it is kept till wanted. The seed is then
taken away from the lower kettle by an opening, and bestowed in bags of
sufficient size to make a cake of 8 lbs. weight after the oil is pressed
out of it. Indeed, the compartments of the heating-kettle are of a size
to contain enough to charge one side of a hydraulic press. These,
therefore, are so constructed as to render the operation continuous, the
upper one being discharged into the under as soon as its contents are
withdrawn to the press. The seed is heated to the temperature of 170
degrees Fahr., when it is drawn off and placed in the bags.

In another form of kettle the seed is heated on a hot hearth, and on the
top of the hearth is a loose ring, within which a spindle revolves to
stir the seed. After the requisite temperature has been reached, the
ring is raised and the seed swept into the bags, which are made of
horse-hair. There is great loss of heat in this method, however, as the
seed is exposed to the atmosphere, which of course cools it.

We now come to the final operation, the mode of expressing the oil. The
screw press we do not need to describe, as it consists simply of two
plates, brought together by a screw, in the same way as the press used
for squeezing apples in the manufacture of cider, and the cheese press.
Let us look therefore at the stamper press. It consists of an iron box,
open at the top, at each end of which are two plates, capable of
containing between them a bag of seed which shall yield a cake weighing
9 lbs. To one of the inner plates of the box is attached a wedge, beside
which is inserted another fi