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and becomes more contracted; consequently, an unequal tension
disturbs the inner crystalline particles, when deranged by the interior
friction of cleaning. Striated tubes should not be used for steam gauges,
as the striated parts will not contract or expand with the parts that
are free from striæ
Front view of the annealing arches, showing three sets of
pans heating each with a separate fire, with the same cylindrical
brick arches and cast-iron doors.
A lear is the term given to an arch, or
oven, open at both ends. Each lear has a small furnace at the receiving
end or side nearest the large Glass furnace; the hot end may be termed
the receiving end, and the cooler the discharging end; the latter
terminates with a chimney, and the hot end is kept at a temperature
just short of a melting heat. The calorie is sustained by oven-burnt
coke, which imparts, decidedly, the most regular heat for annealing,
and is the freest from smoke, the carbon of coal smoke being generally
injurious to the colour of the Glass. There are from two to four of
these semi-cylindrical arches, built side by side; on the floors of
these are placed iron pans to receive the
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