Morning journal and courier. [volume] (New Haven [Conn.]) 1848-1894, 1891-07-31
PROTECTION FROM LIGHTNING,

| The Latest and Rest Methods
| lProf H A. Rowland to Baltimore Sun RePorter.l
Recent scientific study has swept away
| some of the old notions about conductors.
The method now considered the best for
protection of buildings is to provide me-
tai roof, with an ample number of metal
conductors leading to the ground which
will receive and carry off the electric bolts
from the clouds. Copper is the best mater
| ial, but tin or iron will answer the pur-
pose; and 1 always suggest the plscing of
the conductors..a at the corner of build
ing, so that all parts will be equally pro-
| tected.
Though rods may be used, rain sprouts
will answer the purpose equally well. The
physical laboratory of John Hopkins uni
| versity is protected from lightning by the
roof and spouting- You can safely class
| all patented lightning rods as being of lit
tie value beyond conducting rods that any
man can put up himself, because the sim
pie principle underlying all is that the
lightning will follow the best conductor.
The idea so largely adopted in the erection
of lightning rods, that a small band of
passing to a better adjacent conductor,
seems playful. While it is true that light
ming 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 insignifcance as compared
with the method of roofing with a good
conductor. This was illustrated by the in
cident of lightning striking the great mon
aarRr in
The monument is capped with a piece of
aluminium, which has metallic connection
With the ground by means of the iron work
of the interior, but the lightning did not
strike the top of the cap. 1t descended TO
some copper fixed in the side of the pyra-
midal top, some distance from the apex,
burst portion of the stone, and, running
along the copper into the interior, leaped
| without any metallic connection TO the iron
| framework, and passed to the ground. A
| framework of copper rods covering the
| angles, and crossing the sides of the i'm
mense 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 ironwork spoken
of. Somewhat similar to these methods is
that of :he Peabody library. The iron
| shelving connected with the metallic roof.
and resting on stone foundation which
might be shattered by stroke of lightning,
has been connected with the ground by
metal conductors, and no danger from
| lightning is apprehended.
Lightning has no fixed portion of build
| ing to strike. The stroke NAV fall at the
| center of the roof; and while it runs along
the surface of a body, the body may be
broken or crushed BY the enormous pres
sure broaght to bear upon it, in the same
| manner that an explosion of dynamite or
nitro-glycerine would cause fracture. l
have some fragments of a church spire
| struck by lightning, which are bound to-
| gether in their former relative positions,
but exhibiting all the fractures produced
by the conclusion. There is vast differ
ence between the quantity of electricity
and what is known as electrical pressure.
| This is illustrated in a simple manner by
| the compression of air. a small quantity
of air can be compressed to the same de-
gree to obtain as great an expansive force
as large quantity. The quantity of cleo
tricity in a stroke of lightning is not near
ly as much as passes along almost any cleo
trio wire on the street, but the voltage or
electrical pressure of the street wire is
rarely 5000. A volt is the basis on which
the pressure is estimated. The voltage of
the lightning stroke is roughly estimated
at {, 600, 600, 900 volts In addition to this
appalling difference, it may be said that
the current of the wire is constant and
continuing, while the lightning dart is de-
livered in the one two-hundred part of a
second. Such an astounding force is cap
able of doing many strange things.
In speaking of places of safety during an
electrical storm, Doctor Rowland said that
probably as safe a place as any other would
be an iron bedstead, provided the ground
connection is perfect, this being in line
with the above theory, that the lightning
would follow the best conductor.