upport
is fastened just under the end pieces of the frame by hinges. Four
pieces of sheet metal are cut as shown in Fig. 4 and fastened to
the body of the frame with their lower ends hooking over pins
driven in each leg at the proper place. The canvas is stretched as
tight as possible over the two long side pieces and fastened on
the outside edge of each piece with large headed tacks. The legs
will fold up as shown by the dotted line and the cot can be stored
in a small space.
--Contributed by R. J. Smith, Milwaukee, Wis.

** How to Make a Small Geissler Tube [154]

At first this would seem to be a difficult piece of work, yet a
good and beautiful Geissler tube can be made at home in the
following manner:

Procure a glass tube about 3-1/2 ft. long having a hole through
its center about 1/8 or 1/4 in. in diameter, about 1 in. of No. 30
platinum wire and enough mercury to fill the tube and a small
bowl. About 1-1/2 lb. of mercury will be sufficient. The first
thing to do is to seal 1/2 in. of platinum wire in one end of the
tube. This is done by holding the end of the tube with the right
hand and taking hold of the tube with the left hand about 4 in.
from the right hand. Hold the tube in a flame of a bunsen burner
in such manner that the flame will strike the tube midway between
the hands, as shown in Fig. 1, and keep turning the tube so as to
get an even heat. When the glass becomes soft,

[Illustration: Construction of Geissler Tube]

remove the tube from the flame and quickly draw it out into a fine
thread. Break this thread off about 1/8 in. from the long part of
the tube and the end will appear as shown in Fig. 2. Take 1/2 in.
of the platinum wire and slip it through the fine hole made by
breaking the glass thread so that one-half of the wire will be
inside of the long tube. If the end of the tube is now placed in
the flame of the burner, the glass will adhere to the platinum
wire and the wire will thus be sealed in the tube. The finished
end will appear as shown in Fig. 3. This tube as described will be
8 in. long, although nearly any size could be made in the same
way.

Measure 8 in. from the sealed end and place the tube at that point
in the flame, holding in the left hand. At the same time take the
piece of glass that was broken off at the end in the first
operation and hold it in the flame with the right hand. When both
the tube and piece of glass are soft, touch the soft part of the
tube with the