Marshall County independent. (Plymouth, Marshall County, Ind.) 1897-1902, 1899-11-03
Protection from Iirhtninr

monograph on Lightning and the
Electricity of the Air." recently is
sued by the United States Weather
bureau. affords some interesting in
formation upon the question of pro-
tecting buildings from lightning. To
what extent is it practicable to pro-
tect building and to what extent is
1t profitable to attempt such protection
when 1t is practicable? Before an
swering these questions it is necessary
to convey clear idea of the nature of
the lightning flash. The old idea IS
that the flash, like the moderate cur
rent of electricity with which we are
familiar, follows the line of least re-
sistance, and can be diverted by con-
ductOr of a certain size. In this view
the lightning rod is like a channel
made to convey flow of water, and
small channel viii, empty a large reser-
voir if given time enough. But the
Weather Bureau likens the lightning
flash rather to an avalanche, d land
slide down the side of a mountain or
the breaking of a dam-the whole
force is eXerted in one instant and
there is no after current. The flashes,
however, vary greatly in volume, some
of them being mild affairs And it is
always true that a well-constructed
and well-arranged lightning-rod will,
if given time. silently convey away a
vast deal of electricity. thus lessening
greatly, if not preventing, the ultimate
flash. 1t is on this account that light
ming strokes are comparatively infre-
quent in large cities. where lofty spires
and roofs drain overcharged clouds be-
fore the stratum of air between the
cloud and the houses is strained to the
breaking point. 1t follows from the
avalanche-like nature of lightning that
absolute protection of a building is
impracticable unless the building it
self-as being a steel structure-is
itself good conductor. But a very
large measure of protection is within
our reach. A chimney or church sDire
well provided with rods is almost per-
fectly protected and rods distributed to
exposed points will reduce the risks of
a wide roof area as much as seventy
five per cent. There is no definite
AREA of protection" The old rule was
that rod protects a radius equal to it's
height, and the rule may stand for
want of better, but as a matter Of
fact it holds good only with electrical
discharges of moderate volume
Whether it pays in a particular case
to invest money in lightning-rods de-
ponds upon circumstances. Sometimes
the risk is SO slight as to be neglected.
The cost of the rods may be such as to
render fire insurance preferable. But
where the risk of being struck is very
great-as in case of church spires and
high brick chimneys-the value of the
property threatened renders the light
ning-rod a necessity. 1t may be said
to be necessary also where the risk is
less. as. for example, for buildings that
contain a great number of persons
large summer hotels, large school
buildings. asylums and expensive pub
lie buildings. A very costly building
cannot be wisely subjected to a slight
risk from lightning if protection can
be obtained The risk on farm build
ings is greater than on any other class
vi DuIluiHSo, UuI WutIb lUelT value Is
small it is usually preferable to rely
on insurance for projections AS to the
nature of the rod, it is stated that
either iron or copper may be used, and
iron is as good as copper, provided the
section of the iron rod be enough
larger to compensate for its inferior
conductivity. A rod of iron weighing
thirty-five ounces per foot is held to
be equivalent to copper rod weighing
six ounces per foot. A fiat conductor
is recommended. on the ground that
surface counts for more than section
Glass insulatOrs are useless. The rod
may be fastened directly to the build
ing to be protected. The matter OF
greatest Importance is the condition
of the two extremities of the rod-a
matter often neglected with disastrous
results. A rod is perfectly useless-in
fact, a source of danger-if It's lower
end Is not carried down into the