eet of zinc 8-1/2 in. long and 6 in. wide will be
required. This zinc is rolled into a cylinder 2-1/2-in. in
diameter. This will allow for a lap of 5/8 in., which is tightly
soldered only on the outside of the seam. Close one end of the
cylinder by soldering a disk of zinc over it, making a watertight
receptacle. All soldering should be done on the outside and none
of the solder allowed to run on the inside of the seam. All seams
on the inside should be painted with asphaltum in order to cover
any particles of solder. Do not paint any surface, only the
joints. Secure three carbon rods 1/2- in. in diameter and 6 in.
long which are copper plated. Carbons used in arc lamps will do.
File the rods to remove the copper plate, leaving about 1/2-in. of
the plate at one end. Tie the three rods in a close bundle with
the copper-plated ends together and make a contact with each rod
by soldering a wire to the plated ends, allowing one end of the
wire to project about 2 in. for a connection. The plated ends of
the carbons should be covered with paraffin for about 1 in. This
is done by immersing them in a dish of smoking hot melted paraffin
until the pores are thoroughly saturated.

The salts for filling are 1/4 lb. zinc oxide, 1 lb. sal ammoniac,
3/4 lb. plaster of paris, 1/4 lb. chloride of zinc mixed into a
paste by adding 1/2 pt. of water. Form a 1/2-in. layer of paste in
the bottom of the cylinder and place the ends of the carbon rods
on this with their plated ends up. Hold the rods in the center of
the cylinder and put the paste in around the rods with a stick.
Pack the paste in, closely filling the cylinder to within 3/4 in.
of the top. This space at the top is filled with a mixture of 1/2
lb. of rosin and 2 oz. beeswax melted together. This wax seals the
cell and prevents any evaporation. Connection is made to the zinc
by soldering a wire to the outside of the cylinder.

** How to Paraffin Wire [161]

The following description of how to make an apparatus with which
to paraffin wire as needed makes clear a method of construction
that is simple and easy to put together in a. short time.

Secure a pan to be used for this purpose only; one that will hold
about 1 qt. The details of the construction are given in the
diagram, in which P is the pan; B is a base of 1 in. pine; S is
the spool of wire supported near one end of the base by nailing on
standards H and H; F is a spool, with narrow flanges, supported
near the botto