The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1893-09-08
The Largest Search Light in the World.

IL aAlCllC1 DClOLSS OuO AUuUT VI COu-
structing the largest and most powerful
electric search light in the world, now
being set up at the Worlds Fair. Some
idea of its size may be gained by the
comparison made between it and the
men of ordinary height standing by it,
shown in an illustration from photo
graph taken when the search light stood
on the roof of the factory. 1t stands
about 10 feet, 6 inches highato the upper
side of the ventilator on the top OF the
drum, and the total weight is about
5000 lbs, but so perfectly is it mounted
and balanced that child can move it in
any direction. 1t was, built by the Cen
eral Electric Company. The rejecting
lens mirror used in this protector is $50
centimeters, or 60 inches, in diameter.
1t is concave spherical mirror OF the
Mangin type, free from spherical aber-
ration rejecting sensibly parallel beam
of light. It was manufactured especially
for this protector in Paris, France, and is
most perfect specimen of optical work,
three and one-fourth inches thick at the
edges, and one-sixteenh of an inch thick
at the centre, and weighs about $50 lbs.
and the total lens, ring and cover
weigh about ], 600 lbs. This great mirror
is mounted at one end of the big drum,
the outer end of which is furnished with
a door consisting of a metal rim, in which
are fixed number of plate glass strips
f1ve-sixteenths of an inch thick by six
inches wide. Inside this drum and
sliding upon ways arranged onssssthe bot
tom, is placed the electric lamp, the
source of the light which is reflected by
the mirror. 1t is entirely automatic in
its action, is six feet high and weighs
about 400 lbs The carbons used are also
made especially for it. The upper or
positive carbon is one and ope-half inches
in diameter and twenty-five and one
half inches long, with a fve-sixteenth of
an inch core of soft carbon running
from end to end through it's centre.
The lower or negative carbon is one and
one-fourth inches in diameter, is fifteen
inches long and also has core of soft
carbon running through its centre. In
addition it's outer surface is heavily
coated with copper The positive carbon
is set little in front Of the negative,
and thus almost all the intense light OF
the incandescent crater is cast upon the
reflector. The maximum current at
which this lamp operates is 200 amperes,
and at this current the lamp has a lumi-
nous intensity of about 10000 to 100000
candles, the reflected beam a total lumi-
nous intensity of about BIS, 900, 600 candles
an intensity which the eye cannot APP
preciate. In looking at the side of the
beam the spectator only distinguishes
"a stream of light Of comparatively, low
intensity, but in looking. at the beam
directly its brilliancy is fully seen
and the effect is absolutely bli nd
ing. Ventilators at the top and sides
allow constant current of air to pass
through the drum and dissipate the heat
generated by the arc lamp; and they
are SO arranged that no light can escape
through them. All the connections for
adjusting the positions of the carbons
and the lamp are brought through the
drum to the outside, and are arranged in
close proximity to one another at one
side SO that all may be manipulated by
the operator without moving from his
position. Through openings In the drum
covered by densely colored glass the OPP
erationrof the lamp may be watched, and
its adjustments verified. The drum is
supported by trunions in bearings at the
top of a Y-shaped fork, set in base
plate and the whole is supported on a
system of friction wheels, forming turn
table resting upon the top of a massive
pedestal supporting the whole structure.
The drum, fork and base plate may be
either by hand or by gearing provided
for this purpose The drum may also be
elevated or depressed in vertical plane
by similar gearing.
Before the protector was sent to the
Worlds Fair, a public test was made at
Middletown, Conn. From the roof of
the works the great white beam of light
shot forth into the obscurity of the
night, and slowly swept the country side
for miles around, bringing every object
upon which it was directed into brilliant
and distinct relief 1t Illuminated the
roofs of distant villages and scared their
inhabitants, and lighted up the sign
boards miles away, so that they could
easily be read by means of a glass The
protector was turned upwards towards the
sky, and the beam, like a supernatural
divine finger, wrote words upon the
clouds-messages of light to the starry
populations. It was a majestic mani
Hesitation of mans invasion of the realms
of Phoebus.
1t was observed that the space within
the beam was violently agitated, and
closer observation revealed the fact that
millions of moths and minute insects
were lowering in it, attracted by the
brilliancy of the light. Next morning
bushels of dead moths, beetles, other
insects and some small birds, was swept
up from the loof on which the protector
stood They had been killed by the in
tensity of the light.
How far the powerful beam of light of
this instrument can be seen is difficult
to state. The search light set up by the
General Electric Company on Mt. Wash
ington in the White Mountains, has a
diameter of only thirty inches, and re-
flected light from the mirror of about
100, 900 candle power, yet the newspaper
can be read in its beam ten miles away.
How much farther then could this 375,-
900, 900 candle power light be seen in
clear atmosphere free from moisture, if
the protector could be mounted upon an
eminence sufficiently high to clear all
surrounding obstacles?