ON PEINTING TELEGEAPIIS. 
299 
pins. If one of these pins he raised by pressing the key with 
which it is connected, the arm will touch it and slide oyer it in 
passing*, establishing contact with a battery. A wheel on the 
edge of which the letters are engraved, is driven by the clock- 
work which keeps the horizontal arm in motion, and is so 
arranged that whenever the arm passes over the pin corre- 
sponding to a given letter on the keyboard, the letter itself 
on the type-wheel is opposite the paper. If the speed of the 
distant instrument can be so regulated that its type-wheel 
shall move in perfect accord with that of the sending station 
and if the paper ribbon at both stations be pressed upon the 
type at the same instant, the same letter will be printed at 
each. The pressure necessary for printing is produced by the 
current sent by the contact of the horizontal arm with the 
raised pin, which acts upon an electro-magnet and removes a 
catch or detent, permitting the wheelwork to raise the paper 
so as to touch the type. In order to obtain sufficient speed, it 
is necessary that the type-wheel should revolve at least 120 
times per minute ; and it will easily be understood that there 
is great difficulty in so regulating* the receiving machine that 
at this high velocity it shall neither lose nor gain upon the 
sender. The adjustment is obtained by means of a vibrating 
spring which acts as a pendulum, and small differences in speed 
are adjusted before the printing of every letter by the machine 
itself. 
M. Dujardin is engaged in perfecting a type machine on a 
different principle. Want of space compels us to omit the 
description of this and other methods of type-printing* equally 
Methods of automatic transmission have been invented by 
Bain, Allan, Wheatstone, and others. 
In Bain's system the characters are punched out from a strip 
of paper. The perforated strip passes over a metallic roller 
connected to the line-wire, and a spring or brush of wires 
fixed to the battery presses on its upper surface, so that as 
the paper moves forward the wire touches the roller through 
the perforations, sending a succession of currents which re- 
produce the characters at the distant station. A variation in 
the speed of the two machines simply alters the lengths of the 
signs, without in any way confusing the message. This system 
was worked some ten years since between Liverpool and Man- 
chester, at a speed of about seventy words per minute ; but 
owing to the defective insulation of the wires at that period, 
and the difficulty of punching the paper by the imperfect appa- 
ratus employed, it was discontinued. 
Professor Wheatstone has now perfected an automatic tele- 
graph founded upon the same principle, which bids fail* to 
