The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

THE LINE BATTERIES. 487
ADJUSTMENT OF THE LINE BATTERIES.
As to the amount of battery necessary to charge a line of 300
miles there is no fixed rule. It is a question depending upon
the climate, the quality and size of the wire, and the insulation of the line wire. Ordinarily, in good dry weather, a Grove
battery of 60 cells will be sufficient to effect successful operation. If the weather is damp, or the insulation at fault,'the
circumstances of the case must determine the amount required.
It very often occurs on the American lines, that the station at
one end of the line can receive well, and the other end can not
receive anything intelligible. For example, on line A B, 300
miles long, B cannot understand the faint signals received from
A, but at the same time A receives perfectly from B. This diffiA a B
oooooo 300 miles ooo
culty is occasioned, sometimes by atmospheric electricity, but
more generally by faults of the line insulation. The metallic
conductor is imperfect near B. The battery at B becomes active
as a quantity battery. Its quantitative development is plus,
and does not harmonize with the intensity stream coming from
A. One of the remedies in such cases, is the reduction of the
number of cells at B, and the increasing of the battery
at A. I have sometimes found benefit in the polarization of
the batteries to meet the emergency; thus, by placing the platina or positive pole of the battery at A, directed toward B, and
the zinc pole to the earth. The battery at B should also be
reversed. Some experts are of the opinion, that the direction
of the poles have no particular value in the working of a line;
in my experience, I have found the fact to be otherwise, and
entitled to consideration.
If there be an earth connection at a near Bn, the quantitative
development at B will be plus, and in practical service I have
found that it had a retarding or hindering influence of the intensity current from A. The reduction, therefore, of the battery at B lessens that hinderance, and the current from A becomes
more effective. The earth connection at a will carry off a part
of the electric force from A, but if the conductor from a to the
earth be insufficient to lead off the whole, enough will pass on
to the station B, to effect the ends of telegraphing. Suppose
that seventy-five per cent. is carried off to the earth at a, and
the remaining twenty-five per cent. continues on to B, that, or
even a less amount, will be sufficient. Station B, under such a
state of the electrical force, can communicate with A. The