hown in Fig. 1. Bore holes for binding-posts, B, one on
each side of the board, and connect the two wires from the coil to
them. At the other end of the board and in the center drive a wire
nail and attach a small spring, C, to it. The spring should be
about 1 in. long. Take a small piece of soft iron, D, 1/2- in.
long and just large enough to slip freely through the brass

[Illustration: Battery Voltmeter Construction]

tube and solder a piece of copper wire to it; the other end of the
copper wire being hooked to the spring, C. The copper wire must be
just long enough to allow the piece of iron, D, to hang part way
in the end of the coil and still hold the spring in place. A
circular piece of cardboard, E, is slipped over the spring to
where the spring joins the wire. This cardboard is to serve as the
pointer. A piece of paper 1-1/2 in. wide and 2-1/2 in. long is
glued to the board so that it will be directly under the cardboard
pointer and fit snugly up against the top of the coil.

The paper can be calibrated by connecting one cell of battery to
the binding-posts. The iron plunger, D, is drawn into the tube and
consequently the pointer, E, is drawn nearer to the coil. Make a
mark directly under the place where the pointer comes to rest. At
the place mark the number of volts the cell reads when connected
with a voltmeter. Do the same with two or three cells and mark
down the result on the scale. By dividing off the space between
these marks you may be able to obtain a surprisingly correct
reading when connected with the battery cells to be tested.
--Contributed by Edward M. Teasdale, Cuba, N. Y.

** How to Make a Folding Canvas Cot [154]

All the material required to make the cot as shown in Fig. 1
consists of wood 1-1/2 in. square of which two pieces are 6 ft.
long; two pieces 2 ft. 3 in. long; two pieces 2-1/2 ft. long; four
pieces 1-1/2 ft. long; four hinges; some sheet metal and 2-1/4 yd.
of 8-oz. canvas.

Make a rectangle of the two long pieces and the two 2-ft. 3-in.
pieces of wood as shown in Fig. 2, nailing well the corners
together and reinforcing with a strip of sheet metal as shown in
Fig. 3. The four pieces 1-1/2 ft. long are used for the legs, and
two of them are nailed to one of the pieces 2-1/2 ft. long, making
a support as shown in Fig. 5.

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 s