done by heating the end, and at the same time heating the
end of a waste bit of tube or rod; the ends, when placed in contact,
stick together, and a point can be drawn down as before. [Footnote:
"Point" is here used in the technical sense, i.e. it is a thin tail
of glass produced by drawing down a tube.] Having got a point, it
will be found that the thin glass cools enough to allow of the point
being handled after a few moments.

The most convenient way of reducing the point to a suitable length
(say 1.5 inch) is to fuse it off in the flame, but this must be done
neatly; if a tail is left it may cause inconvenience by catching, or
even piercing the finger and breaking off. The blow-pipe flame being
turned down to a suitable size, and the shoulder of the "draw" having
been kept warm meanwhile, let the tip of the flame impinge on a point
where the diameter is about half that of the undrawn tube, and let the
temperature be very high (Fig. 11). The tube is to be inclined to
the flame so that the latter strikes the shoulder normally, or
nearly so. Then, according to circumstances, little or much of the
glass can be removed at will by drawing off the tail (Fig. 12), till,
finally, a small drop of melted glass only, adheres to the end of the
now closed tube (Fig. 13).

Fig. 11.

Fig. 12.

Fig. 13.

Fig. 14.

When this is satisfactorily accomplished, heat the extreme end of the
tube most carefully and equally, holding it in such a position that
the glass will tend to flow from the bead back on to the tube, i.e.
hold the closed end up to the flame, the tube being, say, at 45
degrees to the horizontal. Then when the temperature is such as to
indicate complete softness lift the tube to the mouth, still holding
the tube pointing with its closed end a little above the horizontal,
and blow gently. A beginner almost always blows too hard.

What is wanted, of course, is a continued pressure, to give the
viscous glass time to yield gradually, if it is uniform; or else
intermittent puffs to enable the thinner parts, if there are any, to
cool more, and hence become more resisting than the thicker ones. In
any case a little practice will enable the operator to blow out a
round and even end--neither thicker nor thinner than the rest of the
tube.

Sec. 21. To make a Weld.

To begin with, try on two bits of glass of the same size, i.e. cut a
seven-inch length of glass in half by scratching it with the knife,
a