is left cools and contracts, it is made to suck in the mercury. To
expel the rest of the air, the mercury is boiled in the tube. When
there is enough mercury in the tube to fill it, at as high a degree
of temperature as it is expected ever to go, the end is softened, bent
over, and closed up. As the mercury cools and contracts, it leaves
a vacuum at the upper part of the tube."
As Lawrence stood aside to make room for the
boy, who was stretching another eighty-foot tube, the gaffer continued:--
"Glass beads and bugles are made in much the
same way. Glass of any desired color is used. It is blown, and stretched
into tubes a hundred feet long or more. These are broken up into bits of
the right length for the required bead. To make a round bead, the bits
are put into a sort of mud, made of sand and ashes, and worked about in
it till the holes are filled up. They are afterward put into a heated
cylinder, along with sand; the cylinder is made to revolve, and the motion,
with the friction of the sand, wears down the edges of the softened glass
till the beads become round,-- the sand and ashes in them preventing the
sides from flattening."
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