The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1895-07-07
STREAK OF LIGHTNING
INsTRUMENTs TO PHOTOGRAPH AND
MEASURE AT WASHINGTON.
Estimated $4,000 Horse Power In
Some Thunderbolts-CIoud For-
nation by Electricity.
Philadelphia Record.

Philadelphia Record.
Alexander McAdie. OF the National
Weather Bureau, the meteorologist, who
has for some years been making a special
study of lightning and its effects, will take
advantage of the summer season to con-
duct some unique experiments with at
mospheric electricity. BY aid Of photog-
raphy he intends to make actual models
Of lightning flashes, after first calculating
their lengths, diameters and horse powers.
Three large cameras are every night kept
focused upon the Washington monument.
This high structure, towering to the alu-
tude Of 55 feet. Is looked upon as a tall
lightning rod in itself. Scarcely a season
goes by during which it is not struck by
several Of Jove's unsparing thunderbolts.
Ten years ago it was attacked in this way
five times within twenty minutes, as a re-
suit of which a stone in the upper pyra-
midion was split. Since then. however. the
most complete system of rodding known
has been supplied. The cameras in ques-
ton are posted, one on top Of the Weather
Bureau Building, which instrument is at
tended to by Mr.. Meade himself; one at
the weather station in the Capitol, and the
other at the home of an employe of the
bureau, who lives across the Potomac, a
short distance back of Fort Myer. on the
Virginia side. Each camera is kept con-
tinually focused. so that the negative will
include a high and broad expanse Of sky
In the same vertical plane with the monu-
ment. Telephone communication is had
between the points, and each observer is
under promise TO be on watch at his post
whenever in the night a thunderstorm
threatens to pass over the city. The views,
OF course. must be taken during the dark
ness, that the flash may be distinctly seen.
The watches of the three observers are
carefully compared each day, and the ex-
act time of every exposure will be noted
the , same sed Sasb NAV m oT be ids snaf hesa INV san OF
OF the cameras will be left off during each
nocturnal storm. since the darkness will
prevent the destruction of the plates, As
soon as a streak appears in the field Sc
lected the sudden flash itself makes an in
Simultaneous exposure. 1t will be arranged
that many amateur photographers in the
city may set their cameras for the same
purpose. since each additional view will
add to the completeness of the models
when made.
MAKING THE MODEL.
Having obtained views of the same flash
from the three or more points of observa-
ton. a piece of wire will be held before
each photograph and bent in accordance
with the lines there appearing. The lines
in each View will be bent in the wire so
as to be included in the same plane, and
in this way the model will be an exact rep
resentation of the lightning itself when it
passed from one cloud to another or to the
earth below. as the case may be.
Another interesting part Of the expert
ments will be the calculation of the d.
must be done before the model is made.
All of the measurements of the monument
are definitely known to the fraction of an
inch, and since this high structure will be
visible in the nhnfnUrQnh II raoU he rr1n1
as a scale with which to measure the
length of the flash.
lightning be measured. This to a layman
appears almost like an impossibility. The
lines traced on the negative appear to be
of units of measure, as Tar as their widths
are concerned. But the artful instrument
maker has made provision for this, nor
the actual current Of fire itself. A photo.
graphic enlargement of the original view
may be made in order that the width can
be more easily computed. The proportions
between the length and breadth will, OF
course, remain the same as in the original
negative. The delicate little instrument TO
be used in making the measurement of
cloud diameter is known as the "microme-
ter"
Mr.. McAdie says that no measurement
or attempted up to this time. The flashes
which we commonly see during thunder
storms are anywhere from two hundred
AO~N ~ a AiiAiC IA CAS III Willie THEY
vary as much In d!ameter. The strongest
flash which he ever observed was probably
a foot in diameter. A cross-section of a
thundarbolt would appear as that of a
round iron bar heated to whiteness. The
particles of the atmosphere become white
hot wherever in contact with the electric
fluid.
Mr.. McAdie says that he can devise an
instrument which will foretell a lightning
flash, in order that the photographer may
know when to take his view. That this
can be done is proven by the fact THAI a
telephone bell will ring a second or two
the ringing is caused by the ass same conei-
lions which made the fash itself. The
relative destructive forces of various flash
mathematical formula. Many flashes are
doubtless as much as fifty thousand horse
power in strength.
ATMOSPHERIC ELECTRICITY.
The belief that the formation of cloud
is often accompanied by electrical effects
Is confirmed by Prof. Schuster, who de-
scribes an experience in Switzerland. AS
he was descending from Dent Blanche
after sunset he found himself in a wide
valley at q height Of about twelve thousand
feet. A current Of. air was apparently
blowing up the valley. and below him he
observed the formation OF a cloud at O.
height a little below the snow line. As
night came on and the descent over the
glacier and down the valley was continued,
a series of electric discharges were seen
between the cloud, which was lying in a
deep-cut valley, the sides of the mountain
and the blue sky overhead. The moist air
was evidently flowing through the cloud,
depositing its moisture in the form of drops
and leaving the cloud in an electrified state.
Wherever water rubs against air positive
electricity is generated. Every wave that
breaks into spray under the action Of a
strong wind leaves the water negatively
electrified, the air carrying away the posi-
tive charge. Prof. Schuster suggests that
1t would be of great interest to possess OBJ
servations On atmospheric electricity on
board ship while waves are breaking in the
neighborhood. So far we have TO guide US
only the observations of Exner, who found,
on the Ceylon coast, that the spray from
breaking waves showed by the electrometer
that it was positively electrified.
Three Good Books.
| New York Evening Sim