Port Tobacco times, and Charles County advertiser. (Port Tobacco, Md.) 1845-1898, 1857-08-20

friends. lie was never ashamed OF 1t and
never had reason to be.
From the Valley Farmer.
LIGHTNING RODS.
In former number we stated that to DR..
Franklin belonged the honor of the discove-
ry Of the means of harmlessly drawing the
electricity from the clouds by metallic con-
ductors, and although numerous pretended
Improvements have been made in modern
times, upon the lightning rod, and for which
patents have been granted, we are free to
assert that no real improvement has ever
been made upon the plan first suggested by
Franklin. -.
ALI metals are conductors of electricity,
but some are better than others; copper is
the best, its conducting power being many
times greater than that of iron. Iron is
subject to oxydation or rust, which impairs
its conducting power, but being much
cheaper than copper it is generally used,
and if made of proper size will answer the
purpose. -.,.,.. ..-., ~tr
fla lightning rod or conductor Of suita-
BILE size be properly put up will generally
convey the electricity from the cloud to the
earth harm'zessly, silently and imvisibly, and
although We hear Of numerous instances of
dwellings,, churches and barns being struck
with lightning though they have yet been
provided with lightning rods, this is gene
rally owing to too small rods being used, or
to some defect in the manner Of putting
them up. It might possibly occur in one
time in many thousands that a building
would be struck with lightning though pro-
perly provided with a conductor, where a
cloud in powerful storm should suddenly
approach, SO fully charged with electricity
and coming in so close contact with the rod
that it's conducting capacity would prove in
sufficient to convey the fluid fast enough te
prevent an explosion, but such instances are
extremely rare. ,
Notwithstanding the numerous expert
ments that have been made with electricity,
the question still remains unsettled whether
the conducting power of a rod is in proper
ton to its external surface or to the mass
composing it-whether it travels only upon
the surface or penetrates the pores Of the
metal Franklin assumed that it passed
through the body of the conducting mate.
rial. Some modern philosophers have taken
the opposite ground among these are Pro.
fessor Henry and others. The means by
which they arrive at this conclusion have
never been made public This assumption
however, is in direct violation of established
laws of artificial electricity. Assuming this
ground, hollow tubes have been recommend
ed as a substitute for solid rods, and very
recently patent has been granted for g
new conductor made Of strip of sheet cop.
per, twisted. Patents have also been grant.
ed for various forms of insulators for light
ming conductors. These may be useful te
the small conducting wire of telegraph
over miles in extent, but as they are con
structed and applied to lightning rods they
may be regarded only in the lightof ''hum
bugs" It is well known to those more IA
.miliar with experimental electricity thar
these pretended inventors, that Insulation
afforded to lightning conductors by the ar.
ticles referred to are of no practical value
and as Arago very justly remarks, it is an
"excess of precaution not worth the cost .
j. Murray, prominent electrician OF Eng
land, alleges that nine-tenths of the conduc-
tors in Great Britain are worse than useless,
because of their faulty construction, and this
proportion we believe, more than holds good
in our own country. Incur own native town,
four buildings, within short period, have
been struck with lightning, all Of which
were provided with patent lightning rods
and ansulators, and we hear of similar in
stances every year all over the country.
If the rod be of proper size, and is con-
tinued with perfect joints to the ground, and
the earth be sufficiently humid to afford a
free passage to the electricity, no injurious
effects are likely to ensue. But if the ground
be dry it becomes a non-conductor and the
electricity escapes with an explosion. If
the continuity Of the rod be broken, and the
space between the separated ends is not too
great, the fluid will pass, butsparks will be
emitted at the break, as when you extend
your hand near anybody or substance charg-
ed with artificial electricity. But if the
passing cloud be powerfully charged, de-
feet in the joint will lead to an explosion,
and most likely to disastrous consequences.
We know of numerous instances where
buildings have beeen struck with lightning
in consequence of defective joints in the,
rods