ntly tested for continuity with telephones,
magnetos, or small portable galvanometers. It is only necessary to
ground the conductors at one end and try each wire at the other end. For
this sort of work a telephone receiver used with one cell of some dry
battery is most convenient, and has the additional advantage of
affording a means of communication while testing, and is by far the best
thing for identifying and tagging conductors.

These cables should be frequently tested during the progress of the work
for grounds and crosses with a Thomson instrument, and when the cable is
complete, a careful series of tests of the capacity, insulation
resistance, and copper resistance of each wire should be made and the
exact condition of the cable determined before it is put in service, and
thereafter an intelligent oversight of the condition of the circuits
can thus be more readily maintained.

Where a company has extensive underground service, a regular cable gang
should be in its employ, for quick and safe handling of cables demands
the employment of men accustomed to the work. If the cable has been
properly laid and tests show it to be in good condition before current
is turned on, almost the only trouble to be anticipated will be due to
mechanical injury. Disruptive discharge, puncturing the lead, may occur;
but the small chance of its occurring can be greatly lessened by the use
of some kind of "cable protector," which will provide for the spark an
artificial path of less resistance than the dielectric of the condenser,
which the cable in fact becomes.

If a fault suddenly develops on a circuit, the chances are it will be
found in a manhole, and an inspection of the cable in the manhole will
generally reveal the trouble without resorting to locating with a
Wheatstone bridge. The cable is often cut through at the edge of the
duct, or damaged by something falling on it, or by some one "walking all
over it." To guard against these, the ducts should always be fitted with
protectors both above and below the cable. The cables should never be
left across the manholes, for they then answer the purpose of a ladder,
but should be bent, around the walls of the hole and securely fastened
with lead straps, that they may not be moved and the lead gradually worn
through.

In telegraph cables, when one or two conductors "go," it will probably
be useless to look for trouble except with instruments; but if several
wires are "lost" at once