, 1888-11-08
LIGHTNING STRIKES
TO RELIEVE THE ELECTRICAL TEN
SION OF THE ATMOSPHERE.

tN'A'F
the Flash Takes Place and Why-Cor-
Quoting Currcnts-High Houses.
Now, as n charge of electricity has the
property of inducing another charge of
electricity Of an opposite kind to itself on
any mconlucting,i matter near it, and as
the earth Is composed of what is called
conducting matter, it follows that n
charged cloud sailing over the surface of
the earth induces an opposite charge on
the ground below. These two opposite
charges, one of ''positive" the other of
negative electricity, tend, by another
well known property of electricity, to rush
toward each other and combine. Hence
when they are able to overcome the resist
ance of the air between, which keeps
them apart, they leap together with a flash
and crack, producing the familiar phe-
nomena of thunder and lightning.
Sometimes another CLOUD floating near
the first one takes the place of the earth.
and then the lightning flash takes place
between them. Lightning of this kin
does not strike the earth; but it might
nave n destructive effect on the latter for
all that, because it might give rise to the
"back stroke which is sometimes fatal
to life. The "back stroken is not due to
the direct flash and discharge. 1t is
rather the reaction after the direct dis
Nlltl 5t mas Adhth llhtC tIotN Htlt. sup
pose, for example, that u track of upland
country, a rural district with trees, farms,
and here and there a church dotting it, is
covered by a thunder cloud, which induces
n charge of electricity upon 1t. In order
that the charge upon the earth may get
nearer to that upon the cloud, so as to
combine with it, the electricity, by another
well known property, will heap itself IN
the most prominent and pointed objects Of
the landscape. That is to say, it will ac-
cumulate on the trees, barns, chimney
tops and spires of the district.
The whole atmosphere of the region is
in n state Of tension and suspense. The
bolt is trembling in the balance, but no
man knows where it will fall. Presently
there is n binding flash of light, the Sky
is rent with n lurid stream of fire, and in
stautly the tension is relieved. Tn dis
charge has taken place at one point, the
point which offers the path of least resist
,ance through the air, and at which the
electric tension was most critical. At
every other place where the electricity
had seriously accumulated, there is con-
sequently a sudden fall of electric poten-
tial, or Il collapse to its old condition, or,
rs it is called, a ''return stroke" This
instantaneous change is sometimes as
fatal as the direct discharge, and it may
ruin n building or destroy life several
miles from the scene of the flash. The
return stroke is therefore more mysterious
and unexpected than the flash, but fatal
effects are comparatively rare from it.
Nevertheless, since the latter nave been
attributed to this cause, a person cannot
feel quite safe, although n thunder storm
with lightning is still several miles from
him; the number of miles being estimated
by counting the seconds which elapse be
4tran,, tho Hngh md fha naa1 md allow
ing n distance of four miles for every
second counted. He may feel safer than
if it were close upon him, but there is still
some room for fear.
In fact there is no real safety except
within the area properly protected by q
lightning conductor, or in n building
which is itself n protector, for instance n
sheet iron house. Every building, then,
should be protected in order to be safe.
In the country, where these are often
isolated, n lightning rod would be required
for each; but in towns one rod would
sometimes protect more than one house
around it, according to its height and con-
duCtivity.
The flash takes place at the point of
least resistance, because it is here that the
two opposite electricities can easiest rush
together. But the eagerness with which
they tend to rush together is another
thing to be considered. These two things
taken together determine the discharge.
There may be less resistance to the flash
at one house or tree h at another, but
if the attraction between the opposite
electricities is less at the former, the flash
may traverse the latter house. Hence
one cannot exactly say il one tree or
building will be safer han another. There
is great uncertainty, and this is n reason
for the instinct of W and uncasiness
which most animals feel en- the approach
of a thunder storm.
In general, however, we can say tina
high houses, or those perched on higl
ground, are more likely to suffer from thu
discharge than small low lying houses
The former are therefore all the more eli
gible for protection; and they are to b
avoided in seeking shelter from n storm
So are houses surrounded by trees, an
with ponds or pools of water close besid
them. For trees act as imperfect light
ming rods, having a good earth connection
II especially if they are wet the dis
charge may strike the house in order +
reach the ground through them, or, in tn
case of the pond, through the water. On
should not shelter under trees of an,
kind, but more especially tall, soft tree
like poplars. Many deaths nave been in
CURED from sheltering under poplar tree
in France.
Thunder storms are said to be NOR
frequent in open, t~recless countries, sucl
as the Transvaal or the Scottish hills, an
the fact has been attributed to the un
checked ascent of electrical vapors; bu
on the other hand they are probably les
destructive in such countries.
Chimneys, by creating currents of war;
smoke and by their lining of conductin
SCOT, are dangerous parts of houses, an
fhRr.n MO rNnnNv fnGtar ppu Of tho 1frnEa--
taking that road. 1t were better, then, {
avoid sitting near a fire in a storm. Ii
deed, the safest place in the house on sue
an occasion would seem TO be in the celia
and basement rooms or upon m iron bee
stead. In the open air there cannot be
safer place han n dry hole or ditch, for
places the body below the surface of tn
ground, aud therefore not exposed on
prominent place. But il should be n DIR
lpl1pu- a1sa tbn N,-o+nr Il, q ,,,,- ;,,-;ta -