the closed end, as described. Each succeeding bulb will then be in plain
view during the blowing, and when the open end becomes too short for
comfort, it may be dried out, cut off, and another piece joined to it,
starting as in the first method (Exercise No. 1), but instead of drawing
out the thick bulb to a tube, it is made part of the glass collected for
the next bulb. If the string of bulbs becomes awkward to handle on
account of its length and weight, it may be made in several parts and
these later sealed together by the second method, preferably blowing
through a rubber tube attached to the open end, as described on page 22.

Very neat small bulbs may be made on tubing of a diameter of 3/16 inch
or a little less, but the beginner is advised to start with tubing of
about 1/4 inch diameter. The use of tubing with too thick walls usually
produces bulbs which are thick-walled at the point where they leave the
tube, but inclined to be too thin at the point of maximum diameter
(perpendicular to the axis of the tube) where most of the strain comes
and strength is particularly needed.

CHAPTER IV

ADVANCED EXERCISES

EXERCISE NO. 8

SEALING A TUBE THROUGH ANOTHER TUBE

_First Method--Making a Gas-washing Tube_

This first method can be used whenever one can work through an open end
opposite to the end of the tube where the joint is to be made. To
illustrate it, take a piece of rather thin-walled tubing, about 3/4 inch
in diameter, and some pieces of rather strong tubing a little less than
1/4 inch in diameter. Draw off the large tube in a short cone, then draw
off the tail as in the making of the bulb on the end of the tube, blow
out the little lump slightly, shrink the whole cone a little and blow
gently to form a rounded end like that on a test-tube, with walls about
the thickness of those of the rest of the tube. Cut this tube to a
suitable length, say about six inches, and provide two corks which will
fit the open end of it. Now cut a piece of the small tubing of the
proper length to form the piece which is to be inside the large tube.
For practice purposes, this piece should be about an inch shorter than
the large tube. Flange one end of this tube a little, and anneal the
flange well in the smoky flame. Bore one of the corks so that a piece of
the small tubing will fit it, and cut a couple of notches in the side of
this cork so that air can pass between it and the glass. Pass a short
piece of the sma