The herald., 1912-12-12
THE UNERR|NC sun
It Is Uncle Sans Most Reliable
Lighthouse Keeper.
NEVER FALTERS IN ITS WORK.
sy the Aid of the Wonderful Sun Valve
II Lights the Acetyiene seaeons as u
Sets at Night and Extinguishes Them
as II Rises In the Morning.

The sun is the most trustworthy o'
lighthouse keepers. The sun or Tue
heat from 1t lights many hundreds o'
beacons along our coasts and water
ways evening after evening and eX
tinGuishes them punctually every morn
ing. They are guides on land and sea
that are never touched by human hands
from one months end to another. Iht
way in which the United States gov
eminent, through its lighthouse board
has utilized the services Of the sun and
made that great lamp OF heaven u
faithful and unerring servant is most
interesting.
The discovery of acetylene gas was
the first step toward retiring the lonely
keepers Of the little lights In farofl
places. Modern magic was not sloY
in recognizing the fact that by the ap-
plication Of certain well known scien-
tific principles the lighting Of the great
chains of beacons that girdle the coasts
Of the two seas and the gulf and cover
the great lakes and every navigable
stream in our huge country could be
much simplifed.
The United States did not become in
terested in the acetylene light and its
automatically generating gas buoy until
about the year 1906 and did not adopt
1t until 1908. Then the engineers Of
the lighthouse board devised some
wonderful improvements, among them
the utilization Of the sun.
The self lighting and self extinguish
ing acetylene beacon is very simple
thing, but it depends almost entirely
on the sun valve" which is one Of the
most wonderful but least complex of
the achievements Of modern science.
In the first place. the source Of light
for these lone beacons is dissolved
acetylene, which is stored under pres
sure in steel cylinders. One of these
cylinders can be charged with enough
gas to last small beacon three years
Usually, however, in the case OF float
ing buoys. six months supply is all
that is necessary, as such buoys are
overhaued and painted twice a year.
Knowing the size Of the flame and its
hourly consumption of gas, 1t is very
easy to compute how long cylinderful
will last and how often it will need to
be visited. That Is all the care the
light will need. The sun valve does
the rest
The scientific principle upon which
the sun valve depends Is that light
waves become transformed In different
degrees. according to the nature of the
intercepting body. Sunlight upon dark
surfaces is converted into heat, and
heat produces expansion. This expan.
sion is especially perceptible In certain
metals.
In carefully sealed and substantial
ly mounted glass jar nearly a foot
high and about one-fourth that in d.
ameter thick black rod Is placed per
through the center. 1t is
supported by three slenderer rods of
highly polished copper. The big black
rod Is of copper also and is coated with
lampblack to make it absorb light to
the greatest possible degree The sup
porting rods reflect light without alb.
sorbing 1t and do not expand or con
tract to the same extent as the largest
rod
The thick black piece Of copper in
the center of the jar Is extremely SEN
Sitive to light and heat. AS the sun
appears and the atmosphere grows |
warmer In the morning this rod length |
ems. 1t pushes down into the metal |
chamber in which the glass Jar rests
and touches the end Of q lever. 1t
presses down on this lever, which is
by a spring and cuts Off the
low Of the gas to the lamp.
When the sun disappears from view
n the evening and the temperature of
he air falls the process is reversed.
The rod contracts and releases its pres
sure on the lever, allowing the gas to
low upward to the lamp. The gas Is
gnited by a little pilot fame that Is
never extinguished. Thus the beacon
8 lighted at the proper time and is put
tut when 1t is no longer needed, al.
hough along desolate coasts 1t may
lever gladden. the human eye for
months at a time.
The engineers Of the lighthouse board
ay that the precision Of this device is
Ilmost incredible. 1t can be used with
quail certainty In equatorial heat and
n polar cold, for it responds with the
Utmost accuracy to small variations In
emperature. 1t is used on lonely is
ands in the Pacific. There are nearly
hundred Of these sun valve beacons
q Alaska. In summer they are aids
0 navigation, and in winter they guide
be travellers on dog sledges over the
rozen wastes.-Harper's Weekly.