The Massachusetts spy, and Worcester County advertiser. [volume] ([Worcester, Mass.]) 1825-1831, 1825-08-17
The artS altn &cte1lceS.
For the Massachusetts, Spy.]
LIGHTNING RODS.

Mr.. EDIToR-
read, in the last number Of the Spy,
communication containing several queries in
relation TO metallic conductors. To some of
these will attempt to give satisfactory an
swer.
The writer first asks, " Are round or square
metallic conductors equally good, or are round
ones preferable And what is the most suita-
BILE diameter" | see not why square rod
should not answerthe proposed end, generally,
as well as round one especially, when the
corners of the metallic bars, of which the rod
is constructed, are left as rough and blunt as
we usually find them yet, ifthe square rod be
wrought so exact as to form each corner into
an edge, then think, from established philo-
sophical principles, the square conductor
would not be so good as a round one. The OBJ
iect ofthe conductor is to conduct the. elecrc-
ity into the earth. After it has once received
the fluid, no opportunity should be given it for
escaping before reaching the earth. Points,
we know, will conduct it off much better than
a round body or knob. If then the square rod
be wrought to an edge at the corners, as they
frequently are, each ofthese corners will serve
as continued row of points to conduct off the
fluid into the air, before it reaches the earth.
1t might be we'll therefore to slightly hammer
the corners of the rod, that nothing like an
edge be left.
It was the opinion of Franklin, that large
wire would answer every purpose as a conduc-
tor though, since his time, some bad effects
have been experienced from too small rods.
II would seem that its size should be some-
what proportioned to the number of points.
How large rod one point is capable of filling,
perhaps has never been fully ascertained.
Cd. "Does not the electricity descend in the
internal parts of the metallic rod, the iron be-
ing in every part permeable to lightning as well
as the surlace-and will the electric fluid ever
be visible on the exterior of the conductor un-
til the pores of the rod are flled?" | believe
it is now fully ascertained, that the fluid does
pass down the interior of the rod at least, its
capacity for doing SO is demonstrated by the
following experiment.-Take a metallic rod
Of any convenient length, and les its surface
be coated with some electric, or perfect nom
conducting substance, leaving only small
place, Immediately at the ends, bare. Then
present this, with another similar rod, not
coated, to prime conductor, positively cleo
trifed, and the shock received from the two
rods will be equal. The wax, resin, or with
whatever non-conducting substance the bar is
coated, will not suffer any of the fluid to pass
through it, or upon its outer surface and fiti is
laid so close as to adhere strictly to the exteri-
or of the rod, it must Of consequence pass
through the interior pores. The fluid, being re-
ceived by the elevated points, will undoubted-
ly pass down the interior, and never "be visible
on the exterior Of the conductor, till the pores
of the rod be flled.-By presenting finger TO
lightning rod during thunder shower, Ca dam
gerous experiment perhaps the fluid will pass
in the form of a spark, from the rod to the fin
ger. Now the fluid passed down the exte-
rier, as well as interior, the finger would re-
ceive it imperceptibly, as no reason would be
given for its passing off in a body like spark,
in preference to a continued and invisible
stream.
Sd. " When the house owes its preserva-
&ion to the metallic rod, will there be any ex-
plosion in the atmosphere above, as in cases
when building is struck, having no conduc-
tor, and will the residents be sensible, by the
report and harmless effects, that the rod has
been any defence-or will the attraction and
descent of the fluid be SO gradual and silent,
as to leave no evidence to the inhabitants that
the danger has been averted by the instrument
tality of the conductor?'
We are doubtless inScnsible to the good ef
fects of conductors, when they are conducting
the subtle fluid from the clouds to the earth.
Experiment sufficiently proves that points very
readily and freely receive the fluid; and this
fluid pervades all bodies. Yet sometimes one
body may have more than another, that is,
one be positively, the other negatively cleo
trified. When these two oppositely electrified
bodies come near each other, the fluid will
pass from one to the other in sufficient quanti-
ties to restore the equilibrium; if there be
some good conducting substance placed be-
tween the two bodies, the fluid then passes
through it and restores the equilibrium imper-
ceptibly yet, if there be no such conducting
substance, the electricity in its passage exhibits
luminous appearance, followed by a noise
proportioned TO the quantity of the passing
fluid. Suppose then the clouds to be posi-
lively, ana the earth negatively, electrified.
The instant the cloud approaches so near the
earth that the electricity is attracted by il,
an explosion succeeds. But If there be some
elevated metallic point, when the positively
electrified cloud approaches it, that point will
Immediately receive il, which, being part of
a conductor, and communicating with, will of
course conduct it to the earth. This opera
ton continuing, an explosion is prevented,
and the danger averted by the instrument
tally Of the conductor" without being known
to the inhabitants within the dwelling. When
there is an explosion in the air, if any part of
the fluid comes in contact with the rod, it will
undoubtedly be received by it and conducted