The Owosso times. (Owosso, Mich.) 1897-1926, 1906-09-14
Protection of Buildings From Light

Protection of Buildings From Light
ming.
By Arthur r. Sawyer, b. S., E. E.,
Professor of Physics and Electrical En-
cheering, Michigan Experiment Sta
ton.
This special bulletin is issued to
answer the many-inquiries which come
to the college and station concerning
the function of lightning rods and the
proper methods of constructing them.
1t is now supposed that lightning
flashes are of two distinct characters, a
vertical flash or main discharge between
the cloud and the ground, and side
discharge between the cloud and the
ground, precipita ed as the immediate
consequence of a main flash between
two opposed clouds. An ordinary
lightning rod properly put up is fairly
sure to protect against the first flash
mentioned while to protect against the
second class of flashes would require a
complete "bird cage we'll grounded,
set down over the building 1t is mani
testify impossible to put such a bird cage
over building but we can approximate
somewhat to that condition.
We have the words Of eminent
scientists to the effect that lightning
rods, properly put up, do offer very
material protection, although they dc
not render the house absolutely i'm
mune to injury. Mr. Kellingworth
Hedges. an eminent British authority,
is of the opinion that modern methods
of installing lightning conductors afford
reasonable protection and that the
amount expended on such protection
should be proportional to the value of
the property protected.
The following method of installing
lightning rods is suggested: Let the
rod start from one side, go up over the
building and down the opposite side,
thoroughly grounding both ends as in.
Dictated below. There should be one
rod up each of the two opposite sides OF
any cupola or projection on the roof
the rods to go some two feet or more
higher than the projection and be con-
nected with the main rod. Horizontal
conductors should inter-connect all
vertical rods at the roof ridge level and
also at the ground level. All large
masses of metal in or on the building
should be grounded as directly as posi-
BILE. Gas pipes and all large masses of
m fetal should be kept away from the
lightning conductors. The efficiency
of the lightning rod depends very ma,
terially on its being we'll grounded,
which means that 1t should be in per
manent connection with moist earth.
The usual method of grounding is to
dig hole down to earth that is per ma
hently moist. Solder the lightning rod
to piece of gas pipe or to an old wash
boiler aud imbed this larger metal in
coke. There must be ample carryin &
surface from the surface of the ground
down into this mass of coke. 1t Is sug-
gested that it is well to allow the caves
of the house to discharge the water
through drain tile into this mass OF
coke which is buried beneath the sur
face to keep 1t moist. The only objec
ton to this suggestion is that when a
thunder storm comes up after long
dry spell. the coke is apt to be dry in
spite of this precaution. Any method
that will keep the coke moist or secure
adequate connection between the light
ming rod and moist earth is sufficient
As to the metal Of which the light.
ming rod is to be made, it is suggested
that the choice lies between iron and
copper.
| In any event it should have ample
carrying capacity, if of iron, severa
number six galvanized wires may bt
used or 8 inch galvanized cable such
as telephone companies use in guyine
poles. An iron rod is somewhat more
desirable than copper one because Of
its inductance, but JOINTS are liable tC
rust and the rod deteriorates more
rapidly than does one made of copper
unless very heavily galvanized ant
made of continuous cable. The iron
/ is the better while new but the copper
| is apt to be the more durable.
I