from the mouth, held horizontally in front
of the worker, and gently drawn out to form one continuous tube, as
indicated in _g_. During both the blowing and drawing of this bulb the
rotation must be continued, and both blowing and drawing must be
carefully regulated so that the resulting tube may have the same
internal and external diameter at the joint as elsewhere.

=Discussion.=--In making the original joint, (_a_, Fig. 6), care should
be taken that the lump formed is as small as possible so that it may be
entirely removed during the subsequent operations. For this reason, only
the very tip ends of the two pieces of tubing are held in the flame, and
the softening should not extend more than 1/16 inch down the tube. As
soon as the ends are sufficiently soft to stick together, they are made
to do so. The first drawing of the tube (_b_) should take place
immediately, and reduce the lump as much as possible without making the
adjacent walls of the tube thin. The whole purpose of the rest of the
manipulation is to absorb or "iron out" the lump at the joint. For this
reason, care is taken that this lump is always in the center of the
flame while the joint is being heated, and a small flame is used so
that little of the main tube may be softened. During the first shrinking
of the joint (_c_) the walls next the lump, being thinner than it is,
reach the softening temperature first and are thickened by the slight
pushing together of the ends, so that they taper from the lump to the
unchanged wall. Upon blowing this joint, these thickened walls blow out
with the lump, but as they are thinnest next the unchanged tube, they
stiffen there first. Then as the thicker parts are still hot, these blow
out more, and with the lump make a more or less uniform wall. By this
first operation most of the lump will have been removed, provided it was
not too large at first, and the tube was hot enough when it was blown.
Beginners almost invariably have the glass too cool here, and find
difficulty in blowing out a satisfactory bulb. Under such circumstances
the lump will be scarcely affected by the operation.

During the shrinking of this bulb, the thinner parts of course are the
first to reach the softening point, and thus contract more than the
thick parts, so that practically all of the lump can be absorbed, and a
uniformly thickened part of the tube left as in _e_. When this is just
accomplished, the second bulb must be blown during one or t