44 POWER DISTRIBUTION FOR ELECTRIC RAILROADS.
trouble as nearly as practicable in definite areas and then
to check it in these areas. In the first place the dynamo
connections were reversed so that the stray current would
enter pipes and cables over the most of the system, but
would leave them en route for the negative terminal of the
dynamo only in the districts immediately surrounding the
power houses. ‘Thus it would be certain that the damage
would be limited to known areas which could be attacked
locally with success, instead of being scattered where the
trouble would be hard to locate and harder to remedy.
CAMBRIDGE
EAST BOSTON
P16, 32
Fig. 32 shows the result of thischange. The ‘‘ danger
areas’’ shown here as before by shading on the map, are
comparatively small, although within them the differences
of potential were quite as great as before. Now the prob-
lem was to lead the current back to the dynamo without
compelling it to leave the cables, and corrode them at the
points of exit. ‘To this end, large copper conductors were
extended through the danger area and thoroughly con-
nected at intervals to the telephone cables. The result
was excellent, since the stray currents, instead of passing
from the cables through the earth to the track, took the