Evening star. [volume] (Washington, D.C.) 1854-1972, 1912-01-28

thick. black rod, supported in frame up
held on three slenderer golden rods me
central rod Is really copper, coated Win
lampblack to make 1t absorb light 10 the
greatest possible degree. The smaller
rods. also copper under the polished
golden surfaces, by reason of these sur
faces reflect the light without aosoro-
ing it.
They therefore do not expand under in
f1uence of light, but the black rod does.
Lengthening under the light waves as the
sun appears in the morning, 1t reaches
downward into the metal chamoer IN
which the glass cylinder rests. and there
trolled by a spring. cuts of the now OF
gas through this chamber. to the lamp.
.*
AS the sun disappears in the evening.
the rod, contracting as the heat leaves
it, withdraws its pressure from the lever
which springs back and opens passage
for the gas. A little pilot flame. on duty
all the time at an infinitesimai expense
OF gas, now lights UP tho lamp.
The precision of this device is amazing
and uncanny. And sensitive though IL
is to light, heat and cold in any haDit-
able climates do not disturb 1t. for all Its
parts respond alike to the influence OF
temperature. Hence twenty-one sun
valve beacons are now In operation IN
Alaska, where they serve to aid naviga-
tion In summer and dog-sleish uaVei IN
winter.
Tho best OF lights, however. even acct
ylene, cannot serve all purposes In
fog. There is nothing known TO the
mariner which IL so terrible as FOG. noth-
ing against which he Is so helpless. For
storms and fires and breakdowns marine
engineering has developed resources, but
the fog has SO far been only partially
conquered.
promises soon completely to conquer the
fog. It has already accomplished SO mucn
that the seafaring man speaks proudly
and gratefully of 1t. It's marvel I'M
presses him: its usefulness Is yet more
appealing The captain OF the coastwise
steamer, the steward and the porter alike
tell the passenger enthusiastically or this
new feature Of the vessels equipment.
-.
The only reliable fog signal ever in
vented" said the engineer Of a lightship.
and he pafted his submarine bell at
fectionatsly.
For q long time It was not known just
how uncertain sound signals above water
are They exist on the assumption that
the air carries equally In all directions.
whereas in fact there are different densi-
ties and currents Of air which may inter-
rupt and defect the sound in most UNI
practicable ways. MANY q wreck is the
sad testimony to foghorns heard where
foghorns were not, or not heard where
they were. Bells are much more unre-
liable than horns. Sometimes, indeed, the
lighthouse keeper may not know there Is
a fog offshore. Sometimes, again, II the
fog comes suddenly. disaster may come
with it before the engineer at the signal
station can get up steam.
But now comes master device, which
abandons the uncertain air and makes
the water its medium-water, which is
Of uniform density and sends forth sound
equally in all directions.
A steamer bound from Norfolk to Bos-
ton may run into fog, say some time
before she is due at Sow-and-PigS reef,
that vicious ledge at the entrance to
Vineyard sound. She needs to be sure of
her course here, for the sound is full OF
shoals and contains more than one ocean
graveyard. Or perhaps she sends wire
less to Pollock rip and learning there is
more fog over in Nantucket sound, de-
cides to take the outside course to Bos-
ton.
Let her pick up the signal from the
submarine ben on Vineyard Sound light
ship, just of Sow-and-Pigs. and she has
q safe start at least. Were the whole
coast so equipped at dangerous points. il
is easy to see how confidently the ship
might venture in the thickest fog.
The submarine signal apparatus has
two parts, the bell and the receiver. The
bell is made of a special bell metal, with a
large proportion OF silver in it's compost
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