warm, a small flame is directed by the
blowpipe from the Bunsen flame to a spot on one side of

[Illustration: Glass Blowing and Forming]

the closed tube. As it heats, the air within the tube expands and
becomes compressed, and as soon as the hot spot on the side of the
tube is soft enough, the confined air blows out, pushing the hot
glass aside as it does so, leaving a small puncture. This is to be
enlarged with pointed charcoal until it also flares as shown at B.
This flare is then connected to the flared end of a straight tube,
C, and the T-joint, D, is complete.

Using the blowpipe is not difficult. The lips and cheeks should be
puffed out with a mouthful of air, which is ample to blow a flame
while the lungs are being refilled. In this way, it is possible to
use the blowpipe steadily, and not intermittently, as is necessary
if the lungs alone are the "bellows."

Small glass funnels, such as are used in many chemical operations,
are made by first forming a bulb, then puncturing the bulb at the
top, when hot, with a piece of charcoal, and smoothing down or
flaring the edges. Very small and fine glass tubes, such as are
used in experiments to demonstrate capillary attraction, water or
other liquid rising in them when they are plunged into it, are
made by heating as long a section of tubing as can be handled in
the flame--2 in. will be found enough--and, when very hot, giving
the ends a sudden vigorous pull apart. The tube pulls out and gets
smaller and smaller as it does so, until at last it breaks. But
the fine thread of glass so made is really a tube, and not a rod,
as might be supposed. This can be demonstrated by blowing through
it at a gas flame, or by immersing it in colored liquid. The
solution will be seen to rise some distance within the tube, the
amount depending on the diameter of the tube.

The file is for cutting the glass tubing into lengths convenient
to handle. It should be a three-cornered file, of medium fineness,
and is used simply to nick the glass at the place it is desired to
cut it. The two thumbs are then placed beneath the tube, one on
each side of the nick, and the tube bent, as if it were plastic,
at the same time pulling the hands apart. The tube will break off
squarely at the nick, without difficulty.

The entire outfit may be purchased from any dealer in chemical or
physical apparatus, or any druggist will order it. Enough tubing
to last many days, the Bunsen burner, blowpipe, f