a snaky course (Fig. 151_b_). It makes
no difference in talking-machines whether the reproducing stylus be
moved sideways or vertically by the record, provided that motion is
imparted by it to the diaphragm.

[Illustration: FIG. 151_a._]

[Illustration: FIG. 151_b._]

[Illustration: FIG. 151_c._--Section of a gramophone reproducer.]

In Fig. 151_c_ the construction of the gramophone reproducer is shown in
section. A is the cover which screws on to the bottom B, and confines
the diaphragm D between itself and a rubber ring. The portion B is
elongated into a tubular shape for connection with the horn, an arm of
which slides over the tube and presses against the rubber ring C to make
an air-tight joint. The needle-carrier N is attached at its upper end to
the centre of the diaphragm. At a point indicated by the white dot a pin
passes through it and the cover. The lower end is tubular to accommodate
the steel points, which have to be replaced after passing once over a
record. A screw, S, working in a socket projecting from the carrier,
holds the point fast. The record moves horizontally under the point in a
plane perpendicular to the page. The groove being zigzag, the needle
vibrates right and left, and rotating the carrier a minute fraction of
an inch on the pivot, shakes the glass diaphragm and sends waves of air
into the horn.

The gramophone is a reproducing instrument only. The records are made on
a special machine, fitted with a device for causing the recorder point
to describe a spiral course from the circumference to the centre of the
record disc. Some gramophone records have as many as 250 turns to the
inch. The total length of the tracing on a ten-inch "concert" record is
about 1,000 feet.

THE MAKING OF RECORDS.

For commercial purposes it would not pay to make every record separately
in a recording machine. The expense of employing good singers and
instrumentalists renders such a method impracticable. All the records we
buy are made from moulds, the preparation of which we will now briefly
describe.

CYLINDER, OR PHONOGRAPH RECORDS.

First of all, a wax record is made in the ordinary way on a recording
machine. After being tested and approved, it is hung vertically and
centrally from a rotating table pivoted on a vertical metal spike
passing up through the record. On one side of the table is a piece of
iron. On each side of the record, and a small distance away, rises a
brass rod enclosed in a g