e tape perforations. The rapidity with which the tape may
be driven through the transmitter makes very high speed operation
possible. Of course it is necessary that there should be at the other
end of the wire apparatus capable of receiving and recording the
signals as speedily as they are sent.

As early as 1848 Alexander Bain perfected a system involving the use
of the perforated transmitting tape; at the receiving station the
messages were recorded in dots and dashes upon a chemically prepared
strip of paper by means of iron pens, the metal of which was, through
the combined action of the electrical current and the chemical
preparation, decomposed, producing black marks in the form of dots and
dashes upon the paper. The Bain apparatus was in actual operation in
the younger days of the telegraph. Various systems, based on similar
principles, involving tape transmission and the production of dots and
dashes on a receiving tape, have from time to time been devised, but
have generally not succeeded in establishing any permanent usefulness
in competition with more effective instrumentalities which have been
perfected.

The hardiest survivor of them is the Wheatstone apparatus, which
has been in successful operation for years. Originally the
perforating--or, to use the commonly current term, the punching--of
the Wheatstone sending tape was accomplished by a mechanism equipped
with three keys--one for the dot, one for the dash, and one for the
space. The keys were struck with rubber-tipped mallets held in the
hands of the operator and brought down with considerable force. Later
this rather primitive perforator was supplanted by one equipped with a
full keyboard on the order of a typewriter keyboard. At the receiving
end of the line the messages are produced on a tape in dots and dashes
of the Morse alphabet, and hence a further process of translation is
necessary. This system has proven very useful, particularly in times
of wire trouble and scarcity of facilities, when it is essential to
move as many messages as possible over the available lines.

The schemes devised for combining automatic transmission by the
perforated-tape method with direct production of the message at
its destination in ordinary letters and figures, eliminating the
intervening step of translation from Morse characters, have been
many. Their individual enumeration is beyond the scope of the present
discussion, and would in any event involve a weariso