The Cecil Whig. [volume] (Elkton, Md.) 1841-current, 1891-07-04
THE BEST WAY TO WARD
OFF LIGHTNING.

lowin report of an interview with Prof
Henry A. Rowland of the Johns Hop
kins University, which contalns inter
esting facts relative to lightning conduc-
tors and their uses.
DR.. Rowland SAID Recent scientific
study has swept away some of the old
notions about conductors. The met hod
now considered the best for the protec-
tion of buildings Is 10 provide metal
roof, with an ample number Of metal COZ !;
ductors leading to the ground, whic Ii
will receive and carry off the electric
bolts from the clouds. Copper is the best
material, but tin or iron will answer the
purpose, aud | always suggest the plant
ing of the conductors al the corners of a
building, so that all parts will he
equally protected.
Though rods may be used. rain
spouts will answer the purpose equally
we'll. The physical laboratory of the
Johns Hopkins University is protected
from lightning by the root and spoutiLg.
\ on can safely class all patented light
mig rods as being of little value beyond
conducting rods that any man can put
up himself, because the simple principle
underlying all is that the lightning will
follow the best conductor. The idea SO
largely adopted in the erection OF light
ming rods, that small band of glass
will prevent tie electric current from
passing to better adjacent conductor,
seems play full. While it is true that
lightning is attracted to an elevated point
or angle, when you cast your eyes over a
city like Baltimore and see the large
number of such points and angles, the
use of pointed rods fades into insiguifi
canoe as compared with the method of
roofing with "a good conductor. This was
well illustrated by the incident of light
ming striking the great monument in
Washington several years ago. The
monument is capped with a piece OF
aluminium which has metallic connec
ton with the ground by means of the
iron work of the interior, but tue light
ming did not strike the top of the cap.
1t decended to some copper fixed in the
side of the pyramidal top some dis
lance from the apex, burst a portion off
the stone, and, running along the copper
into the interior, leaped without any
metallic connection to ths iron Frame
work and passed to the ground. A frame.
work of copper rods covering the angles
and crossing the sides of the immense
cap was recommended by me at that
time for the future protection of the
monument and has probably been con
structed. The ground connection Was to
be through the internal iron work spoken
of. Somewhat similar to these methods
is that of the Peabody Library. The
iron shelving connected with the me-
talic roof, and resting on stone founda-
ton which might be shattered by a
stroke of lightning, has been connected
with the ground by metal conductors,
and no danger from lightning is appre-
hended.
Lightning has no fixed portion of a
building to strike. The stroke may fall
at the centre of a roof, and while it runs
along the surface of body, the body
! may be broken or crushed by the euor-
| nous pressure brought to bear upon it,
in the same manner that an explosion OF
dynamite or nitro glycerine would cause
| fracture. have some fragments of a
| church spire struck by lightning which
are bound together in their former re-
| fractures produced by the conclusion.
| There is a vast difference between Il g
quantity of electricity and what is known
| as electrical pressure. This is illustra
| ted in simple manner by the com
preston of air. A small quantity of all
can be compressed to the same degree
to obtain as great an expansive force as
a large quantity. The quantity of cleo
| trlcity in stroke Of lightning is not
| nearly as much as passes along almost
| any electric wire on the street, but the
voltage or electrical pressure Of the
street wire is rarely 3 900. A volt is the
basis on which the pressure is estimated.
The voltage OF the lightning stroke is
roughly estimated as 5000, 000,0 volts
In addition to this appalling difference il
| may be said that the current of the wire
is constant and continuing, while the
lightning dart is delivered in the one
| two hundredth part of a second. Such
| an astounding force is capable OF doing
many strange things. A volt may be
rated as equivalent to the pressure Of au
electrical door bell"
In speaking of places of safety during
an electrical storm DR.. Rowland said
that probably as safe place as any other
would be an iron bedstead, provided the
ground connection is perfect this be-
ing in line with the above theory, that
the lightning would follow the best con-
ductor