The Cecil Whig. [volume] (Elkton, Md.) 1841-current, 1875-07-24

| same time. In fact, music in any form is
one of the greatest additions to the social
pleasure of home.
STRAW LIGHTNING CONDUCTORS.
Straw is about the last material one
would think of using for lightning rod
but according to a French journal, it an
swers the purpose admirably. 1t had been
| observed that the straw had the property
of discharging Leyden jars without spark
or explosion, and some one in the neighbor-
hood of Tarbes got the idea of construct
ing lightning conductors, which were form
ed by fastening wisp or rope of straw to
deal stick by means of brass wire, and
Gaping the conductor with a copper point.
1t is asserted that the experiment has been
tried on a large scale around Tarbes, eigh-
teen communes having been provided with
such straw conductors, only one being
erected for every 60 arpents, or $50 acres,
and that the whole neighborhood has thus
been preserved from the effects. not only
of lightning, but of hail also. The Jour-
nal Of the Society Of Arts says: This state
ment comes from respectable source; and
the apparatus being extremely simple and
inexpensive, it is at any rate worth the
trial. Copper conductors are out of the
question in ninety-nine cases out of hun
dred, but every cottaser almost could set
up straw one''
To the Editor Of the Scientific american
On reading the above account of straw
lightning rods which you sent me, made
the simple experiment of measuring the
electrical resistance of a small bundle of
straws, and found it to be very high in
deed, say a million or two times as great
as copper wire of the same size. This
really disposes of the question of useful
ness for lightning conductors; for, not to
mention other considerations, with such a
resistance as this, the straw rod, if struck,
would be instantly ignited, if not even
blown to pieces by an explosive combus-
ton.
The real question of most Importance to
a rod is, however, not what will become of
it after it is struck, but, strange as it may
sound when first stated, what certainty
there is of its being struck. Thus: Sup
pose it to be proved that given rod if
struck would carry to the ground all the
electricity entering it, but that this same
rod was far less likely to be struck than the
adjacent gable of the house: What use
would such thing be as protection?
Evidently we have first to consider the con-
ditions which will secure the striking of
the rod in preference to any thing else
near it, and then it will be time to inquire
as to its capacity to carry off the fluid
when it gets it.
l have already indicated, on a previous
occasion, and you have ably discussed, the
very simple conditions involved in this first
and most important problem. Briefly they
are these: that the lightning rod should
offer path to the earth presenting many
hundred times less resistance than any of
the neighboring accidental paths, made up
of metal pipes, rods, nails, bolts, hinges,
stove pipes, cutters, and the like, inter-
spersed with woodwork, human beings,
and other destructible matter. The cleo
trio fluid, when it finds presented to it two
equally good roads, impartially divides
itself and sends half its substance by each
route. If it finds two routes where the
distractions or resistances are as one to
for Tor &c
itself by the easy as by the difficult road.
In order that rod, therefore, should keep
all of flash to itself, it must offer i'm
mensely superior inducements in the way
of conduction to the ground. If it does
this, then it is an absolute protection to all
around it, and not otherwise. Now expert
ment has proved beyond question that
the conducting power of given substance
varies with its cross section or weight per
running foot; and therefore, when we take
rod of some good conductor, such as cop
per, and make it thick and connect it thor
oughly with the earth, we get an easy path
to the earth, for any cloud collected cleo
trio fluid. What we must do, moreover, is
to make this path so easy that no chance
road shall come any where near it for east
ness.
Under the existing state of affairs, with
the large quantity of metal used in our
buildings, this can only be done when we
have either very thick rod or its equiva-
lent obtained by uniting the rod near the
roof to the very water, gas, and other pipes
which would otherwise be its rivals. A
conductor fulfilling the above conditions
will always be easily able to carry all the
electricity that strikes it. We constantly
see recommendations of this or that form
of rod because it has more surface, and
electricity of high tension travels chiefly on
the surface. Grant that this last statement
applies in full force to lightning, yet we
see that it is of no practical Importance.
Increase of surface will not diminish resist
ance or improve conducting power. This
we know by countless experiments, and the
opposite is not even claimed. If, therefore,
certain rod has not substance enough in
it to make it an efficiently good conductor,
squeezing or twisting it into any possible
form will not do it any good in the direc-