The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1870-07-04
lightning Rods

The essentials of good rod are that 1t
shall be we'll and firmly set, having points
above the highest portions Of the building,
and enough OF them to protect all the salient
places that it shall he solid to the ground.
or, IL made in joints, firmly united. 1t
bable amount Of fluid falling upon it.. Not
more than two separate points should JON
one stem to the ground, and the lower ter,
minus must 60 far enough into the ground
to reach moist earth IL the ground END mas
several branches. it is all the better; Ii
placed In he'd Of charcoal it is still better.
rs that is gooo conductor, and also pre-
vents rust to some extent.
The conducting power Of copper Is tnur
or five times that OF iron. and that fact has
led to the manufacture Of light copper rods,
which have not substance enough to with
stand the heat, and SO melt when ScFcrci!
tested. Some manufacturers assert tiat
nothing better than halt-inch iron ROD mas
yet been devised, and that substance Is ~
much needed as surface to constitute hrs'-
class conducting ability
1t is very uncertain. how large an area
rod of a given height will protect. DlItcrcht
French electricians have rated II as clrcu-
lar spacc of a radius from one to three times
the height of the rod above the highest part
of that to which it is attached, but little
confidence can be placed in these conclu-
sions.
The electrical conditions Of the atmos-
phere arc not uniform, and the discharges
may move so rs not TO be Influenced by Il
rod. Discharges may occur iaterally-sllcn
have been known to pass horizontally
through the atmosphere great distance
and strike with the most destructive Ylo-
lcnce intervening or opposing objects: one
mast of a ship has been struck, while an
other taller one, which had - rod attached,
was untouched. These facts, however, IN
stead of furnishing arguments against RODS,
only illustrates the importance. OF having
all the exposed points protected.
BY n great multiplication of conductors
the accumulation Of electricity is silently
built cities, ships clustered at the wharves,
large quantities Of iron in warehouses, ETC.,
etc. are seldom struck, because the cleo
tricai equilibrium is maintained silently.
liza metal rod were extended from cloud
to the earth, no lightning would be seen.
because the fluid would pass and repass and
the equilibrium be preserved. Clouds
passing low over cities lose their electricity
silently-by the church spires usually.
Isolated prominent objects are most fire.
uuently struck. Single trees. detached
houses, barns, haystacks. and the like, SUI
fer oftenest. Practical men and rod manu-
facturers say that lightning strikes three
times rs often i'm the country as in town, in
proportion to the number of buildings, and
that ten'rods are used in the country to ono
in the city, in proportion to the houses.
Ascending currents Of air from chimneys.
drafts of air through open windows and
doors, sharp edges and corners of elevated
= cornices, the "peak" of roof, or mai
protruding, furnish favorable points fol
lightning to drop upon under iavoring cir
cumstanceS.
Metal stands to electricity simply in the
office of conductor. 1t furnishes rs natu
raj channel tor it to flow in rs the bed o
river presents to water, and hence the
utility of lightning-rod is sclf-evident
Keep the points bright, the fastcnings insu
lated, the connections perfect, have it wei
set, avoid q small wire when good mass 0
metal is needed, and All investment in Il roc
will be judicious one.
1t is also suggested that they be placed
upon that side of building from whicl
thunder-storms most frequently approach
Buildings with high combustiblc stocks
very tall structures, or high flue stacks
should not be without lightning protectors
An ordinary fire policy covers losses from
fire caused by lightning. The mere shat
tering of Il house by wind, lightning, earth
quake, or any other violence, is not covered
by an insurance policy, but burning is
EnUineeT.