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On the other hand, each separate pencil must have a distinct 
wire, perfectly insulated from the rest, so as to reproduce only 
that part of the drawing, or message, over which it passes. 
Thus, originally, when it was proposed to produce elaborate 
copies like those of Caselli, an enormous number of wires were 
needed. This idea was subsequently abandoned, and the 
number of wires reduced to eleven, and lastly, to five. The 
message is set up in ordinary type, and is placed upon a truck 
moving upon a miniature railway. The chemically-prepared 
paper is laid upon a metal plate, carried on a similar truck. 
Over the truck carrying the type ( t ) is fixed a species of comb 
the width of the letters, having five teeth, arranged in such a 
manner that when the carriage moves, the comb shall pass 
over the face of the type so as to touch their raised surfaces ; 
and over the truck at the distant station is a similar comb, 
with the same number of teeth, resting lightly on the prepared 
paper (iv ) . Each tooth of the combs is connected by a separate 
and insulated line- wire, so that when any one of the teeth of 
the sending-comb touches a part of the type, a current is 
transmitted, which produces a corresponding mark upon the 
prepared paper, as is shown by the diagram. 
The trucks are started at the same moment by the release 
of detents connected with electro-magnets, and are drawn 
forward by weights. 
When all the five line-wires are in good order the system 
admits of marvellous rapidity, and the fac-simile given in the 
plate will show that legible despatches may be forwarded even 
when they are partially deranged. 
As the blue mark of Bain and Caselli is produced by the • 
dissolving away of the iron pencil, the ferrocyanide solution is 
not applicable to Bonellfis system, for it is necessary the teeth 
of the comb should wear equally; the teeth are therefore 
formed of platinum, and the solution is nitrate of manganese, 
which does not act upon the platinum. 
The inventors of the automatic systems consider that 
messages may be prepared by the sender himself, at his own 
office, and handed to the Telegraph Company simply for 
