Make two of these—­one for each end.

[Illustration:  Details of Canvas Cot Construction]

The hinges are attached as shown in Fig. 5 and the whole support 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 end of the glass and draw the tube out into a point like that shown in Fig. 4.  Break off the piece of glass, thus leaving a. small aperture in the long tube.  Seal the remaining 1/2 in. of platinum in this aperture in the same manner as before being careful not to heat the tube too suddenly.  The tube is now ready for filling and the upper part will appear as shown in Fig. 5.