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POPULAR SCIENCE REVIEW. 
means of a flexible copper wire, connect a steel pen fixed in a 
wooden bolder with tbe copper of the battery. The pen will 
now be found capable of writing in blue upon the prepared 
paper ; but if either wire be disconnected from the battery so 
as to cause the current to cease, the pen will cease to mark, 
the power to do so being entirely dependent upon the passage 
of the current. 
In Bain's telegraph the ribbon of moistened paper is carried 
forward by clockwork over a metallic roller, thus : — 
A pencil of iron wire rests upon the paper, and is so connected 
that the positive current flows from the iron to the paper, 
producing signs similar to those of Morse. 
The apparatus we have described is so simple and so easy to 
manage, that it will always be extensively used; nor is the 
peculiar alphabet as great a disadvantage as it may seem, for 
there is no real difficulty in acquiring’ a knowledge of it. 
The instruments which print in ordinary letters by the pres- 
sure of inked type are extremely complex, and though, from the 
fact that each letter is formed by the simple pressure of a key 
like that of a pianoforte, it might seem they are easily worked, 
the fact is, so much skill is required to manage them and 
to print at a sufficiently high speed, that they are at present 
practically unremunerative. The most important instrument 
of this class is that of Professor Hughes, of New York. The 
apparatus at all the stations is precisely alike, and consists of 
a keyboard like that of a pianoforte, containing as many keys 
as there are letters, figures, and marks of punctuation to be 
printed. Connected with the keys is a set of movable pins 
arranged vertically in a circular frame, through the centre of 
which passes an upright shaft, kept constantly revolving by 
clockwork. Hinged upon this shaft is an horizontal arm, 
which sweeps round continually a little above the circle of 
