St. Landry democrat. (Opelousas, La.) 1878-1894, 1892-12-31
POPULAR SCIENCE NOTES.

Will t)!dNtcI VI IdEiS.
The EFFICACY OF LIGHTNING RoDs,-
: Snow Harris, perhaps, went more thor
0 oughly INTO the question of the relation
D OF the form of the conductor to protcc
e than any one else. He experiments;
2 considerably, but as matter of fact de
, rived his best information from cxtensiv
study of the effects of actual flashes them
selves rather than from laboratory work
and IN this, in the long run, he PROVED
himself wiser than Faraday. For Fara
day, IN 1850, seeing only the question 0
, conductivity in the problem, said decid
edly that this was a simple question o
conductlvlty, and that Surface die
nothlng--the solid section was the es
sentlal consideration. The weight OF
Ills deservedly great fame settled the
questions upon his basis for many wears
although Harris, with the records Of
years before him, knew that whatever
theory might seem to demand: the facts
were plain that surface area was of great, i
not equal Importance with solid section
in dealing with lightning discharges. Blu,
the public meanwhile was drifting some
what into the position cf that old Brit
ish Admiral, who being called upon t.
approve some specifications for a..Iightnins
conductor upon a certain III clubhouse,
although himself believer in the sur.
face theory of Harris, yet thought he
would go down and consult Faradav
about the matter. Now Faradav said
very positively that the solid rod was
better than the tube (which would gise
greater surface with less copper, that
solid volume was everything, superficial
area nothing, and that if Harris says
otherwise. then ''he knows nothing what
ever about it!"' The Admiral straight.
! way approved tho solid rod conductor
for'the lighthouse. Within day or so
ne met Harris, and instancng the matter
! the latter said: Surface area is the most
important. and if Faraday says other
wise, then he. knows nothing whatever
about it" 'If lightning is a discharge
OF an oscillatory character" SAYS DR..
Lodge, "and some of us think that it is.
then the theory Of the lightning rod. as
regards all that section below the point,
requires alteration''
OF course, in places, this view of the
character of the flash is at variance with
the decision of the Lightning Rod Con
ference; and in consequence thereof
discussion fnow famous) occurred at the
British Association meeting in 1888. The
honors seemed to be about evenly d.
vided. for while Lodge had undoubtedlv
the clearer insight into the character OF
the lightning flash, the decisions of
the Conference were not success.
fully assailed the attitudes of the
Conference and Lodge seem to me to be
somewhat like the positions of Faradav
and Harris. If the reader is contemplate
ing the erection of rod, these points
may be of service to him. Get good
iron or copper conductor; if the latter,
that which will weigh about six ounces
to the foot. and preferably in the form of
tape; if iron is used, and it is, perhaps
if anything the better have it in rod or
tape form and weighing about thirty-fvc
ounces to the foot. The nature of the
locality will determine to a great degree
the need of a rod Places apart but a
few miles will differ greatly in the rela-
tive frequency of flashes In some local.
ties the erection Of a rod is imperative;
in Others needless. The very best |
''ground' you can get is after all for
some flashes but a very poor one, there
fore do not imagine that you can overdo
it in making good "ground." If the
conductor at any part of its course goes
near water or gas mains it is best to con
meet it with them. Wherever one metal
approaches another it is best
to connect them metallically. The neigh
Dorhood of small bore fusible gas pipes
md indoor gas pipes in general, should
De avoided. " lLodge.) The top of the rod
should be plated, or in some way protected
rom corrosion and rust Independent
grounds are preferable to water and gas
mains. Clusters of points or groups of two
n three along the ridge rod are recon-
nended. Chain or link conductors are
If little use. Without doubt for al
most all flashes good lightning rod
veil earthed is the appropriate path to
arth, and the rod may be relied upon to
0 act at the proper time. Any part of
building, if the flash be of certain char
cter, may be struck, whether there is
cd on the building or not. Fortunately
his is the rarely exceptional case, the
rcat majority of flashes ia these ATTITUDES
eing comparatively mild, and not at all
$ dangerous as we are apt to imagine
hem to be. We have instanccd several
asses where editices seemingly amply
rejected have been struck below the
DDS mot to be COMPOUNDED with cases
t defective rods, etc. J; and it is now ;
ecoming plain to us how lparadox of
aradoxe9 building may be seriously {
by lightning without having
cen struck at ALL Take the famous
Iotel de Ville of Brussels, so we'll pro, :
,cted by Melsens's method-we might =,
Id, perhaps, the best protected build
g in the world-against lightning, and
It it was damaged by fire caused by
nall induced spark near escaping gas.
uring the thunderstorm some one flash
arted up "surgings" in piece of metal a
vt connected in any way with the pro. I
ctive train of metal. The building /
obably "did not receive" says DR.. 7
odge, ''even a side flash, yet the in =
iced surgings set up in it, induced by c
axwell and Heaviside's electromag-
tic waves, were so violent as to ignite
me gas and cause small fire. y
lmerican Meteorological Journal. II
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