The sun., 1912-07-14
Nn10R RACES sMTS4oRbhoMr sTARaxM
Hrt4hton Iieach Psrk We'd. Sat. and Sun.
Eights at 40.
Admission. 98r. Grand Stand. SOc.

easily distinguishable at a distance OF
1000 yards. The most powerful source
OF artificial light In general use at the
present time is an electric arc taking n
current OF $50 amperes. There are more
powerful lamps which take even as much
as $50 amperes. but they arc not in general
use. The l50 afnpere lamp is generally
placed at height no greater than sixty
feet, at which elevation II makes avail
able less than half the candle power rep
resented by the rays Of the full moon.
This amount was frst increase by
plocing a conical mirror beneath the
iamp. Still large part Of the light was
wasted, many Of the rays being reflected
int o the sky. where they were useless to
the observer This led to the invention
OF the present almost barrel shaped
PROTECTOR The interior mirrors con-
dense the light into beam which is very
pow erful and spreads only slightly.
The PROTECTOR can be rotated. lowered
or elevated at WILL SO that any desired
area can be gone over with this tremen-
dous beam.
Although glass is n material which will
take a very good polish and is for thnt
reason always now used for searchlight
mirrors, il was long time before il was
poss ible to manufacture glass parabolic
| mirrors with any degree OF accuracy.
Hence for somo time mirrors OF this form
were made Of metal. the particular metal
being an alloy known as specuium metal
| About the year 1874 Mangin found that
II a spherical mirror instead OF being
of uniform thickness throughout We're
made in the form Of concavo-conveN
lens, thus making ii thicker at the edges
than in the middle. there was practically
no spherical alteration.
This was n great advance. and the
MapQin mirror came very much TO the
fore. Ten wears later. however, Schuckert
was successful in his endeavors to make
, a parabolic mir or out OF one piece OF
Qlaes and after that the glass paraholic
mirror became 1he mirror IN prac'ice
as we'll as In theory. -,
, There Ia, perhaps. no property OF the
searchlight more important than its
capability OF throwing a powerful and
concentrated beam OF light in any par; pd
beam IL not always the most desirable;
There are times when a beam Of light well
spread out over large area would DC OF
, very much more use.
Take, for instance. the case OF steamer
irving to pick up buoy. II Ia not very
diificIlt to see that with a concentrated
, beam having quite a small amount OF dis
, , persion II would in most cases take more
time in spite OF the more powerful light
than il would with less powerful light
, spread ont over a larger are,. Having
/ once spotted the buoy the concenira,ed
beam could with advanta ge be used TO fol-
low IL up. TO provide this dispersed beam
a diyerging lens or dispenser IL used;
l This consists of numl er OF cy indrical
| lenses mounted In metal ring. The di-
r rect ion OF the rey is net interfered with in
, the direction Of the axis Of the Iers. ut
ia the direct ion at right snTies to the
: axis the ray il refrncted or lent in pre-
= isely the same manner rs in the case of
q an ordinary spherical lens. The result
IN that instead of coma Of ight having u
4, focal point there is Wedge o1 heht
' with focGl line.
One particular type OF sePr"hlifht
= that used in the Sucz Canal, IL especially
l interesting to Panama building Ameri-
n cans. The Suez Canal regulations stipu J.
. late that the protector shal! be capable
. OF giving the required hight under two
= different conditions. In the first case
y when no vessel Ia approaching Il con-
n centrated beam Of light uninterruptsdiy
. required,
On the approach Of vessel being
: noted. though, the concentrated fepn
n in order that the nav igation Of the APP
a proarhing ship may not 'e in'rrier'd
. with must le split up in the following
'. manner Tho engo ot divergence of th'
beam m,,st remb,n unalteied thar II
I tho width must he the sam" ~ thct ~ TIN
a concentrate beam. ~ there must tc 4
dar., interval of Ave degrees oStert IN t''
middle Of the beam. This dart n.orN -
:. IL, Of course. to prevent those IN 'hor.'
.! the srrrosch!ns 'cGfc, 'c'"" ,"N
= porariiy blinded, with results winch rAi
I be mag gincd better than described