Repeat the operation of heating and blowing
at least three times.
Join a No. 4 and a No. 2 tube in the same way.
Experiment 55. To make a large hole.
Take a piece of No. 4 tube about 6 inches long,
close one end, smooth the other, and allow it to cool.
Now to make a large hole in the side of this
tube, proceed as follows: Heat in the blowpipe flame the point at which
you wish to make the hole, and blow a slight bulge (1,
Fig. 75). Then heat the top of this bulge until it
is red hot over an area about equal to the size of the hole you wish to
make, and blow hard to make a thin bubble (2, Fig. 75).
FIG. 78
A REPEATING AIR GUN
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Break away the thin glass of the bubble,
smooth the edges, and the hole is made. The edge of this hole will
project beyond the side of the tube (3, Fig. 75). If
you wish to make the edge even with the side of the tube, heat it in
the blowpipe flame until it shrinks back level with the tube.
FIG. 79
FOUR-WAY JUNCTION
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Experiment 56. To make a tee.
Take a piece of No. 4 tube about 6 inches
long, close one end, smooth the other, and allow it to cool. Take
another piece 3 inches long, close one end, and allow it to cool.
Now make a hole in the side of the first tube
at a point 3 inches from the closed end. Do this as described in
the last experiment but leave the hole projecting beyond the side of
the tube (1, Fig. 76).
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