New-York tribune., 1905-06-26
PROTECTION FROM LIGHTNING.

Referring to the recent discussion in these col
umns of the usefulness of lightning rods, "The
Poughkeepse Eagle" mentions a theory adj
vanced by the late Henry Bentley, of Philadel-
phia. His belief was that a metal roof Of
fered adequate protection against thunderbolts.
The supposition seemed to derive value from
the fact that Mr. Bentley was the president Of
a local telegraph company. "The Eagle" adds
that its own Independent observation for sew
eral years has tended to confirm Its faith in
the correctness of the doctrine.
Obviously, the desirabity Of having lightning
rods must be determined by experts. 1t does
not clearly appear that Mr.. Bentley was one.
His duties may have been OF an executive nat
ure mainly and not essentially scientific From
the character of his responsibilities he would
probably acquire a superficial familiarity with
one class OF electrical phenomena, but that
might not enable him to dispose wisely of
technical problem presented by electrical phe-
nomena of another class. On the other hand,
the so-called Lightning Rod Conference of 1882
was a body made up of the leading specialists
in the United Kingdom and its verdict has
accordingly been accepted as one Of the most
trustworthy that it was possible TO obtain any
where.
So. too. when fresh research was undertaken
by committee of British architects in 19O1,
the cooperation of such distinguished student
of electricity as Sir Oliver Lodge was Invited
The INQUIRY thus initiated which extended over
a period of four years, was devoted cmeny TO
finding cut whether there were exceptions to
the rule and deciding how to account for them
! The committee whose report appeared only
few weeks ago, reviewed the exceptions, but
reaffirfned the advice given by experts twenty
three years previously-tO use properly con-
! structed lightning rods. 1t then went on 20
specify what notifications in the design and
! connections seemed to be dictated by recent
| experience Even with these the lightning rod
is not to be considered infallible; but the large
degree of protection which 1t affords makes its
adoption wise especially for small buildings.
The chief trouble encountered during the last
! few wears seems to have been with factories
| and other large edifices.
There is in the metal roof theory possible
| defect which we venture to point out. 1he
nurpose that must be accomplished In enc man
| nor or another is to render innocuous charge
Of atmospheric electricity which passes from
| the cloud to the earth in close proximity TO a
building The general principle to be adopted
| and we imagine that Mr.. Bentley would nave
| assented to this-is to lead the current off by
| an easy path. and not leave it to take one that
world work injury Metal, being good con-
! ductor of electricity ought to serve much bet
fer than wood, brick or stone. Now, how snail
| the metal be disposed? A conductor Is worth
less unless it forms a part Of a through route.
| Phil trolley wheel half an inch away from
the copper filament which usually fits into Its
! grooved periphery, and thereupon two or three
! miles of overhead wire, the return route for
the propelling current (the rails) and the motor
rnder IL, car will all be rendered absolutely
| halnIess without &C Slete system of con-
| +acts there will be no flow of electricity. Ii
metal roof is made Il link in the chain by
| nronerly connecting it with the vertical con-
ductor If NAV play part In leading the light
ming to the earth, but how could any electricity
which once found its way into metal roof get
out again if a continuous route to the moist
oortb were not afforded? To encourage light
ming TO take the path it ought to follow and
to entfce it away from chimneys, gables and
| similar architectural projections, it has been
daaned expedent to offer to the sky the
temptation of a metallic point reaching several
rppt above the highest detail of the structure
m ha enarded A fiat roof extends no such in
vitation. 1t may be harmless but it seems
TO be doubly disqualified for useful service IN
conducting lightning to the ground.