145. It is sometimes required that the iron thus produced
should not be of uniform thickness throughout. This is the case
in bars for railroads, where greater depth is required towards
the middle of the rail which is at the greatest distance from the
supports. This form is produced by cutting the groove in the
rollers deeper at those parts where additional strength is
required, so that the hollow which surrounds the roller would, if
it could be unwound, be a mould of the shape the iron is intended
to fit.
146. Vermicelli. The various forms into which this paste is
made are given by forcing it through holes in tin plate. It
passes through them, and appears on the other side in long
strings. The cook makes use of the same method in preparing
butter and ornamental pastry for the table, and the confectioner
in forming cylindrical lozenges of various composition.
Of copying with altered dimensions
147. Of the pentagraph. This mode of copying is chiefly used
for drawings or maps: the instrument is simple; and, although
usually employed in reducing, is capable of enlarging the size of
the copy.
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