, 1888-01-20
LIGHTNING STRIKES
TO RELIEVE THE ELECTRICAL TEN
SION OF THE ATMOSPHERE.

quently Fatal "Rcturu stroko"-where
the Flash Take Place and why-Con-
Quoting Currcnts-uiEh Houses.
Now, as n charge Of electricity has the
property Of inducing another charge of
electricity Of an opposite kline to itself on
any conducting 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
nnce Of the cir between, which keeps
them apart, they leap together with n 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 dash takes place
between them. Lightning of this kind
does not strike the earth; but 1t might
have 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 stroke is not due to
the direct flash and discharge, 1t is
rather the reaction after the direct dis
charge has taken place elsewhere. Sup
pose, for example, that n track of upland
country, n 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 it. In order
that the charge upon the earth may get
nearer to that upon the cloud, so as TO
combine with 1t, the electricity. by another
well known property, will heap itself on
the most prominent and pointed objects Of
the lsndscape. That is to say, it will nc
cumulate on the trees, barns, chimney
tops and spires OF the district.
The whole atmosphere of the region is
in II state Of tension and suspense. The
bolt is trembling in the balance, but no
man knows whore it viii fall. Presently
there is n binding flash of light, The sky
is rent with n lurid stream Of fire, and in
stantly the tension is relieved. Thc dis
charge has taken place Mt one point, the
point which offers the path of least resist
ancc 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-
scqucntly n sudden fall Of electric poten-
tial, or n collapse to its old condition, or,
as 1t is called, n return strokc.n This
instantaneous change is sometimes as
fatal as the direct discharge, and it may
ruin n building or destroy life several
AllllNo lAhlil llle NlNlt u lllt lllAl. / Nc
return stroke is therefore more mysterious
n unexpected than the flash, but fatal
effects are comparatively rare from 1t.
Nevertheless, since the latter have been
attributed to this cause, n 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-
tween tho flash and the peal, and allow
fnR ~ 1fCNnF.nA Af TOM rAf1.H To- ,..a~.
second counted He may feel safer than
Fit 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 n
lightning conductor, or in u building
which is itself a protector, for instance a
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 cnchi but in towns one rod would
sometimes protect more than one house
around it, according to its height and con
ductivity.
TIL flash takes place at the point OF
least resistance, because it is here that the
two opposite elcCtricitics can easiest rush
together. But the cugcrnCss with which
they tend TO rush together is another
thing to be considered. These two things
- 3D. ''NNA INV wv NAA"NAANll ~
There may be less resistance to the flash
at one house or tree than Mt another, but
If the attraction between the opposite
electricities ia less at the former, the flash
may traverse the latter house. Hence
one cannot exactly say il one tree or
building will be safer than another. There
is great uncertainty, and this is a reason
for the instinct of awe and uneasiness
which most animals feel on the approach
of n thunder storm.
In general, however, we can say that
high houses, or those perched on high
ground, are more likely TO suffer from the
discharge than small low lying houses.
The former arc therefore all tho more eli
gible for protection; and they are 10 be
avoided in seeking shelter from q storm.
So are houses surrounded by trees, and
with ponds or pools Of water close beside
them For trees act Us imperfect light
ming rods, having g good earth connection,
and especially 7 they are wet the dis
charge may strike thu house in order TO
reach the E1Z1l through them, or, in the
case Of the plll through the water. One
should not shelter under trees Of any
kind, but more especially tall, soft trees
1ike poplars. Many deaths have been in
CURED from sheltering under poplar trees
in France.
Thunder storms are said to be more
frequent in open, ~treeless countries, such
rs the Transvaal or the Scottish hills, and
the fact has been attributed to the I'M
checked ascent Of electrical vapors; but
on the other hand they are probably less
destructive in such countries.
Chimneys, by creating currents of warm
smoke and by their lining Of conducting
SCOT, are dangerous parts Of houses, and
there are many instances Of the discharge
taking that road. 1t We're better. then, to
avoid sitting near Il fire in n storm. In
decd, the safest place in the house on such
an occasion would seem to be in the cellar
and basement rooms or upon an iron bed
stead. In the open air there cannot be n
safer place than a dry hole or ditch, for it
places the body below the surface Of the
ground, and therefore not exposed ON a
prominent place. But it should be n dry
hollow, else the water in it may invite the
discharge; for water, being Il conductor in
good connection with the earth, lowers
the resistance TO the Observation-Disclosures
ing.
BraZils Diamond Mines.
a gentleman who returned from the
diamond districts of Brazil recently SAYS
that the stories of exhaustion Of these