ost of this
would be lost in a coarse screen, hence the necessity of employing as fine
a line screen as practicable in order to get as much detail in as possible.
It is mainly on this account that a 5" x 4" print is recommended, as, if
fairly bold subjects are used for copying, the small detail (this is, of
course, a very vague and indefinable term) will not be too fine, and the
time required for transmitting reasonable. For obvious reasons it is a
great advantage to put the print under pressure to cause the glue image to
sink into the soft metal base and leave a perfectly flat and smooth
surface. It is essential that the bands on the print lie along the axis of
the cylinder, so that the stylus traces its path across them, and not with
them.

We have now an arrangement that is capable of taking the place of the key
K, Fig. 4, and the diagram, Fig. 11, gives the connections for the complete
transmitter. A is the aerial, E earth, T inductance, L ammeter. The closed
oscillatory circuit consists of a spark-gap G, inductance F, {23}
[Illustration] and a condenser C. The secondary J of the coil H is
connected to the spark-gap, and the primary P is in circuit with the
mercury break N, the battery B, and the local contacts of the relay R. The
action is as follows. When contact is made between the stylus Z and the
drum V by means of the conducting bands on the line print, the circuit of
the relay R and the battery M is completed. The closing of the local
circuit of the relay R actuates the second relay R', allowing the primary
circuit of the coil H to be closed. As soon as the primary circuit of the
coil is completed sparks pass between the electrodes of the spark-gap G,
causing waves to radiate from the aerial. The duration of the wave-trains
radiated depends upon the duration of contact made by the relays {24} R and
R', and this in turn depends upon the width of the conducting strip that is
passing under the stylus. The battery M should be about 4 volts, and the
battery D about 2 volts. The two-way switch X is connected up so that the
relay R' can be thrown out and the key K switched in for ordinary
signalling purposes. If any sparking takes place at the point of the
stylus, a small condenser C' (about 1 microfarad capacity) should be
connected as shown. In the present instance the condenser should be used
more as a preventive than as a cure, as in all probability the voltage from
M will not be sufficient to cause destructive (