The Massachusetts spy, and Worcester County advertiser. [volume] ([Worcester, Mass.]) 1825-1831, 1825-08-03
For The Massachusetts Spy.1
LIGHTNING RODS.
Mr.. EDlToR-

Nlfts A-DlAOI-
Considerable has been written concerning
the utility of Metallic Conductors and the
frequent disasters occasioned by lightning. rem
der the subject daily more and more interest.
ing. One author lays it down that the Con.
ductor, to guard the house, should consist Of a
rod without breaks or dscontinuities. between
one fourth and one half of an inch thick. if If
be Of iron, but smaller, if it be brass or conner.
terminating, upwards in sharp point, about
four or five feet above'the highest part of the
building and all, believe, agree, that the
point OF the stem should be of pIalina. cold. or
Siiuer.-Auother writer saws, the top should he
made Of round, smooth iron, at least three quar-
tiers OF an inch IN diameter, and when it can
be conveniently done, instead of linking, should
be smoothly 'DeIded together; but when, by
reason OF Its length, or otherwise, it is iucon-
venient to weld the whole rod, let il be smooth
ly connected by screwing the end Of one part
into the end OF the others. There should be five
or more points, one in the centre, perpendicu-
lar, and the others, oblique. They should be
fled to a sharp, slender point, and TIPPED
with silver. The point should be elevated. at
least, five or SIX feet above the highest part OF
the building.
A very recent publication, (said TO be Pro-
lessor Silliman's,) asserts, that the stem of a
lightning rod effectually defends circle OF
which it is the centre, and whose radius is
twice its own height. building sixty feet
square requires a stem fifteen or eighteen feet.
raised in the centre Of the roof-one, 100 feet
square, stem of 80 feet. To protect two
chimnies, Of equal height, with one rod, the
height of the rod, above the chimney on which
it is raised, should be equal to halfthe distance
between the two chimnies. This same writ
er goes on to say, that great proportion of
the Lightning rods, now erected in this coun-
try, are useless, or nearly so, not being con-
structed and set up on true philosophical prin-
ciples.
Experimental philosophy is more satisfactory
than theoretical, and those who have tested
principles ny practice, may give the most sound
information on those subjects. | will suhlon
a few queries, and will sincerely thank you,
or any OF your correspondents, to explain and
answer them, and describe lightning rod
and the manner of its erection, that will most
etlectually subserve the purpose Of its forma-
ton.
LIST. Are round or square Metallic Conduc-
tors equally good, or are round ones prefera-
BILE And what is the most suitable diameter,
Cd. Does not the electricity descend in the
internal parts of the metallic rod, the iron be-
ing in every part perneable TO lightning, as
well as on the surface, and win the electric
fluid ever be visible on the exterior of the
conductors, till the pores of the rod are filed
Sd. When house owes its preservation TO
the metallic rod, will there be any explosion
in the atmosphere above, as in cases when a
building is struck, having no conductor, and
will the residents be sensible by the report,
and the HARMLESS effects, that the rod has been
defence--or will the attraction and de-
scent Of the fluid be so gradual and silent, as
to leave no evidence to the inhabitants, that
the danger has been avcrted by the instru-
mentality of the conductor
9TH. Is itnot Objectionable TO have the stem
of lightning rod ascend beside Of, and adhere
to chimnies-and what philosophical objection
could be raised to the rod being perpendicu-