New-York tribune., 1874-07-30
DO LIGHTNING RODS PROTECT

THE DIFFERENCE BETWEEN INSULATION AND IsOLA-
uoN-THE PRESENT CoNTRIvANCK DANGEROUS.
To me Editor Of The Tribune.
SIR: My brief note with its somewhat
startling inquiry g. Do lightning rods proectp has
complished the object sought by provoking much
needed discussion upon very important subject Some
OF the communications have been very instructive and
saluary. and will spread abroad rational and
tegent views upon the snDiect. correct much
mlsapprehensOn and also TO direct attention 20
instances where creduous people have been done"
out Of their money and lulled into false OF
security, while in fact their peril has actually
augmented by the very smeasures they have been
duced TO adopt for safety. did not state, of
correspondents represents that the rod referred
TO was first class but. that It considered, that
by people generally, by those were experts
did say, however, that the glass insuators and
ringed spikes were " all in good condition" After a
more recent and careful examination, will say
that large majority Of the lightning protectors
upon buildings throughout the country, we're originally
better safer nor perhaps, than this one.
and but few of them to-day In better condition.
Waving as comparatively unimpOrtant my own
panaton OF the peculiar phenomenon the
Astoria incident, and also ignoring the hy-
pothetca assumptions of of your
spondents who hppanty venture to account
for the whole phenomenon without even comprehend
ing of the circumstances, and who, perhaps
consciously distort significant details III order
sustain their own conclusions will return to the only
really vital question: Do lightning protectf II 50,
should they be insulated or mott
Most Of the rods common use are said to be I'm
sulated" when in fact they are but isolated. would
make distinction between these two terms Insuia-
ton consists in interpOsIug between conductors
conducting medium or barrier arranged so as to render
practically impossible for the current TO pass from
conductor 70 another This be done thoroughly
by coating the conductor with absolutely non
nH
terposng nou-conducng body the purpose of pre-
venting local contact OF different conductors with each
other. Glass rings and the like should therefore be
class fled isOlators, not insuiators. the Atlantic
cable is insulated. believe II is generally conceded
that during electrical storm the earth is charged
with negative electricity, while the clouds are charged
with positive electricity In the efJrt TO restore an
equilibrium the tendency the current TO pass rom
the positive negative pole side therefore from
the clouds downward, not from the earth upward
Under ordinary circumstances building like the earth
upon which rests charged negatively and attracts
inmates sufficiently say the building Is "strucK,
ind greater or less damage ensuing according 10
the facility with which the current ls transmitted 10 the
great negative below the earth II IL meets
with considerable resistance during It's transit that ls II
terposing OF less damaged according
10 their lack OF conducting capacity OF pSweI OK dn
proportion they offer 20 TINS tendency
toward the establishment OF an equilibrium rake
mousse charged negatively bearing isolated rod com
mon glass Z" InsuatOrs' IN drcucing storm ana you
have the conditions peril absolutely increased FOR Tue
projecting charged negatively Oy lts connection
with -nc earth. attracts more less strongly tue posi-
i've current fro above and the latter may be so SUD
denly and freely delivered 10 Overtax the receiving
capacity of the rod TINS there is danger or te
currents passing surface OF the gas. rings
poorer conductors anJrued py tne ndVerlas
which the house is composed. among when WIZ So
ect that presenting the least resistance and teh
proceed It's way like lightning demonstrating De-
yOud cav the fact that isolation rs Inadequate Or pro-
lection Take the OF house bearing ample nsh
completely insulated by non-conducung
jackets. shall nnd that, While no rellei Is az
electric tension negative dlHtension eA
stlng in itself. such conductors 90 anord
increased facilities for relieving the surcharged CLOUDS
their Load and, although the house may Do summed
situated proximity 70 the spot where the cnaree
eu,ers the earth The root such building paTtcu-
larry II metallic, should be directly connected ny good
conductors with moist EARTH IN order tat IL ma
not become surcharged negatively. This brings me 10
the nal query IL it necessary advisable 10 lnsu
'nChnng-rOds' asllg do not hesitate ~ aVow thit
nv recent nvesti cations have satisfied me tat Dulu
iucs NAV be rendered safe By dlscardlng lnsula
ton altogether and providing ample highways OF some
nOu-cOrrOsiVe metal such copper, anOrdg saIcleht
surface area which the currents may ireey tFel
20 and fro with such OF communication prop
erV extended above and below, promoting the ifeest
Dgssiuc circulation comparative safety Is atJahaoe
but from tue miserable and dangerous contrvances III
TOO common use steadfdstiy pray, good Lord denver
/ "a H. +iNi'"A'''
Nelr-T TOrL. JIIy 9s. 1874.