or
8 in. in length, as the maker prefers, and bundled to a diameter
of 7/8 in. The wires may be straightened by rolling two or three
at a time between two pieces of hard wood. If the amateur has
difficulty in procuring this wire, the entire core may be
purchased ready-made.
After the core wires are bundled, the core is wrapped with one or
two layers of manila paper. The straighter the wire the more iron
will enter into the construction of the core, which is desirable.
Beginning half an inch from one end, No. 16 cotton-covered magnet
wire is wound from one end to the other evenly and then returned,
making two layers, and the terminals tied down to the core with
twine. Core and primary are then immersed in boiling paraffine wax
to which a small quantity of resin and beeswax has been added.
This same wax may be used later in sealing the completed coil into
a box. Over this primary is now wrapped one layer of okonite tape,
or same thickness of heavily shellacked muslin. This completed
primary will now allow of slipping into the hole in the secondary.
Should the secondary have been purchased without a case, a wooden
box of mahogany or oak is made, large enough to contain the
secondary and with an inch to spare all around, with room also for
a small condenser; but if it is not convenient to do this work, a
box like that shown in Fig.
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