The New Orleans bulletin., 1875-09-26
PROTECTION AGAINST LIGHTNING.
At this season of the wear certain class OF

| FkUIECI1ON AGAINSI LlGHIN1NGs
At this season of the year certain class o
men, not overscrupulous in their dealings
are in the habit of doing thriving trade
These men invariably start upon their mis-
sion with the first thunder storm of autumn
and follow in its track all over the country
Every death from lightning recorded in any
part OF the Union serves as an invaluable
advertisement to their business, and they
reap rich harvest out of the fears which
thunder and lightning inspire. Their STOCK
in trade, it need hardly be said, consists o
lightning conductors. We do not mean te
imply that this business is not as Legitimate
as any other. On the contrary, we regard
those who are engaged in any way in the
work of affording to society that protection
discoveries guarantee, as benefactors to the
race What we say is that a large number Of
persons are employed in this business who
are more desirous of making money than they
are OF spreading true knowledge of science
among their customers All the science they
recognize in their transactions is that which
brings in the largest amount of profit, and to
accomplish this desired end all their inventive
faculties are set in motion. The falsest scien.
tiic theory which favors their purpose in this
respect is sure to be patronizsd; the most cor
rect will meet with little favor if it is adverse
| to their interests.
As with most other articles offered for sale,
| the impression generally prevails that the
more expensive the lightning rod which is
| attached to building, the more efficient it
| will prove when struck with the electric fluid.
This belief on the part of the public admira-
bly, serves the purpose of a class of traders
referred to, since it affords them an opportu-
nifty of bringing all manner OF devices into
play in the construction of lightning con-
ductors SO as to increase the price. Stars,
tubes and crosses, and variety of compli-
Gated Inventions have been introduced into
the cross sections, upon the theory that light
ming travels only upon the surface of metallic
conductors.
Nor are those engaged in this business
wholly responsible for this false theory. 1t
has been either upheld or permitted to pass
current by many writer's on the subject, and
has arisen from mistake which is commonly
made of confounding static with dynamic
electricity. Perhaps it would be more cor
rect to say that it is to be attributed to an en-
tire Ignorance of the real properties of the
electric fluid When electricity is in motion
it is dynamic, when at rest it is static. 1t has
been we'll ascertained that when it is at rest it
always tends to diffuse itself upon the surface,
and this knowledge led to the belief that
electricity in motion followed the same law.
The experiments of the most eminent sci
entific investigators, however, have long since
demonstrated that when electricity is in mo-
ton it is conducted, not in the ratio of the
surface of the metallic rod, but in proportion
to the quantity of metal it contains. This
was determined by taking cylindrical wire
OF certain size, and measuring the resist
auce it otf4red to current of electricity, and
then 1attenlng the wire and ascertainipg the
amount of resistance it offered in this con-
dition. The resistance in both cases was
found to be equal, although the extent of
surface presented in the latter instance was
much greater than in the former. This
proved conclusively that the conducting
powers of metallic bar depended upon the
quantity of metal it contained, and not upon
the extent of surface which it presented An
other method of demonstrating the truth of
this theory is by taking a strip OF
gold leaf about half an inch wide and two or
three inches in length, aud passing
through it a moderate charge from
a six-jar electric battery. In this |
case the gold will be entirely burned |
up. But if piece of gold nire one sixteenth |
of an inch in diameter be used instead of the |
gold leaf, though in presents a surface only |
one fif III of the former, it will carry off the
most powerful charge that can be obtained |
from the same battery without suffering any
damage The different effects of static and |
dynamic electricity have also been ascertained
by similar experiments, when it was found |
that piece of gold leaf was capable of sus-
tanning very heavy charge of electricity so
ong as it was allowed to rest in state of
equilibrium; but the moment it became dy-
namic by flowing off through the same me-
lium, the gold leaf was destroyed.
The result of scientific investigations has
demonstrated, therefore, that the efficiency of
/ metallic rod depends upon its weight per
.oot not upon the extent of its surface. 1t
matters not whether it be round, square or
,abular, provided the metal be present in
'uffi cient quantity. Wire'and wire ropes, or
lat ribbon conductors, are perhaps most
because of the great facility with
which they can be placed il position.
The necessity of protecting buildings
gainst the danger of lightning is universally
and while it would be sheer folly
o neglect such an obvious precaution, it is
veil to bear in mind that the most elaborate
nd expensive lghtning-rod is of no more
-alue when struck with the electric fluid than
he piainest pattern of conductor, provided it
contains an equal quantity of metal.
A strange case of mistaken identity was before
he Exeter (England) magistrates the other day.
: woman named Knight was charged with break
ng pane Of glass. The chief constable said
he accused had been convicted of felony in 1867.
ie called an inspector to corroborate this who
aid he himself took the charge, and he had
nown the woman from child. She protested
er innocence, but the p lice insisted that she
as the person mentioned in the police book
reduced. It. was, however, afterward found
hat the police were mistaken, and the chief con- ,
table apo 'ogized to the woman, and the magis- !
rate accepted his explanation.