The Stark County Democrat. [volume] (Canton, Ohio) 1833-1912, 1898-04-28

cave lens backed by silver and hardened
vulCanite. Until recently the work Of
grinding a mirror was a longer task than
at present. But machines for grinding
have been perfected, so that mirror, IL
work were rushed upon It, could be turned
out in about week, but If the manu-
faCturor had all the time he would like he
would take two or three weeks.
The searohlight mirror is not q modern
invention or discovery. The use of con-
cave lenses reaches back to the days when
ATChimodes Is said to have burned up q
Roman fleet beseRing Syracuse by plac-
ing two large cOnCaye lenses on the city
walls and focusing the suns rays on the
hostile vessels The seaTChlight mirror Is
simply an application Of the concaye lens
to increase the power of the electric light
All cruisers, battleships and torpedo
boat catohers are provided with one or
more such lights. The size and intensity
vary, according to the service required.
In diameter the projectors, or cylinders,
range from 1S to 80 inches and in length
from 2 to 3 feot The common arc light
of the street consumes about ten amperes
Of current and is rated ut 1,20O candle
power. The largest searohlights used by
this government require 80 amperes and
therefore should have something like 10, e
600 candle power. This matter of light
measurement, however, is complicated
thing, and the case Is modified greatly by
the employment Of the parabolic mirror
In clear weather the beam thrown from
a ships searchlight can be seen Is or 20
miles away A person into whose face 1t
Is projected, when five or six miles away,
Is likely to find 1t rather dazzling. The
white sails Of a schooner thus Illuminated
can be perceived with glass from the yes-
sci employing the light 10 or 10 miles off,
But the chief use to which this appara-
tus Is put by warships Is the detection Of
torpedo boats. Not only are those very
small craft, with little superstructure, but
they are painted to look like the ssa-dark
gray, dark green or a kindred hue. OF
course an object OF this class could not be
discovered at any such distance as ship a
canvas. No torpedo boat is expected to
become visible, even II the beam of q
Eearchlight is thrown squarely upon her,
more than two or three miles away. In
deed 1t takes wonderfully keen eyesiRht,
powerful marine glass and oontinu
sweeping Of the searohlight from side to
side to detect such an assailant single
mile away.
The nearer the boat comes to the ship
which she seeks to attack the greater are
the chances Of discovery, but when she is
only mile of she needs only three min
ntes-hardly that-to come close TO the
vessel and launch torpedo, and that is a
very short time in which to train light
rapid fire gun on her and sink her Wide
differences of opinion prevail among naval
experts regarding the value of searchlights
In hunting torpedo boats
The operation Of the light Is a simple
matter. The machinery which controls 1t
Is located In the base, or stand, on which
the lamp Is plaCed. This base contains
two motors, one OF which controls the YER
tical DETECTION Of the searchlight and the
other the horizontal.
The operator may regulate the position
Of the light from any place on board the
vessel. 10 Is only necessary that the OBJ
server shall stand without the rays The
best position Is below the lamp and little
to one side Of IT, II an observer stands In
any part of the rays, 1t 10 ouriously true
that he can sec nothing on which the rays
bear.