The record-union., 1898-10-28
On Metallic Structures In Whole or in Part
Of Suhtenanaan Character.
Tests Made by A. A. Knudson
Showing That the Escape of the
Electrical Current From Over
head TroI1eys Exercises a DAM
aging Influence on Elevated
Structures and Water Pipe Sys-
tenn of New York City.

NEW YORK, Oct. PA. A Knudson
read a paper before the last meeting of
the American Institution of Electrical
Engineers on vagrant electric currents
and the vast amount of damage that
may be inflicted by them on all metallic
structures in whole or in part of sub
terranean character.
Mr.. Knudson showed as a result of
exhaustive tests made by him that the
escape of the electrical current from
overhead trolley eXerciesd Il damaging
influence on the elevated structure and
the system of water pipes in the upper
parts of the city.
He also showed that currents escap-
ing from trolley lines in Brooklyn found
their way into all the lower sections OF
New York, affecting by electrolysis not
only the pillars of the elevated roads,
but possibly the very anchorages of the
bridge itself. He recommended that
legislative action be taken to check the
danger, declaring that unless regula-
tlons were adopted the life of public
property would be greatly shortened.
Dealing with the results of electro
iytic action on the terminal rails of the
trolley system, it was found that
large amount of metal had been re-
moved by electrolysis, the bottoms Of
the rails having been cut down to knife
edges for several feet back of the ends.
1t was also found that in many in
stances the tie rods and cross bars,
which keep the rails in position, had
been eaten entirely through
In describing one of the most remark
able of his discoveries Mr.. Knudson
said: Coming down the west side of
the city L was surprised to encounter a
full-fiedged trolley current in the ex-
treme lower part of the city.
THE first intimation was found at
Rector and Greenwich Streets, it be-
coming more pronounced in the vicinity
of South Ferry, where, in testing be-
tween the rails of the Metropolitan
Gable Road and an elevated pillar.
variation of one-thirtieth to eight thr-
tieths volt was found, the rails posi-
tive, and the samefreading between the
rails and the water pipes.
After making further tests the cur
rent was found to come from the
Brooklyn bridge. Having pointed out
how an overhead trolley, using the
water pipes and incidentally the rails
as return can spread it's influence for
twenty blocks north and south, the
existence of this current through the
bridge is accounted for"
The very serious question presented
itself. he continued, in what condition
might we expect to find the anchor
bolts and the iron foundation of those
pillars, for, previous to any use of cleo
tricity on the bridge, it had been known
that currents were escaping over that
structure from trolley lines in Brooklyn
and, passing over, would find their way
through the city by underground pipes.
and thence recrossing the river, arrive
back at the power house in Kent ave-
nue..
In conclusion he said: at appears 10
be the duty of engineers to exercise
every precaution against the effects Of
this invisible element of destruction,
which, if left to itself, will certainly
shorten the life of valuable city prop
erty.
1.-The damage already done by elec-
trolysis to public works in England has
led to the establishment of regulations
to prevent such action in the future
and similar leg -slation may be expected
in this country if these conditions be
allowed to continue. Prevention is
''The incandescent light currents 1 do
at the moment on account of their light
not consider as particularly dangerous
voltage, but, it having been established
that the fraction of a volt difference of
potential will cause electrolytic action,
it simply comes down to a question of
time when these straying incandescent
currents will have to be seriously con-
sidered.
1t is my opinion that ordinary cau-
ton would suggest that periodical tests
should be made in every city where
trolley road using a. ground return is in
operation. In this way threatened
damage by electrolysis to water and
other pipes as well as to bridges mighg
be arrested and finally controlled"