The daily Alaskan., 1913-01-15

| By the Aid of the Wonderful Sun wave
 N Lishts the Aestylsne eeacons oa lt
 Sets at Night and Extinsuishss Them
 asIt Risss In the Morning,
 The sun is the most trustworthy of l lighthouse keepers. The sun or the ! heat from 1t lights many hundreds or beacous along our coasts and water ways evening after evening and eN- l tlngulshes 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. The way in which the United States gov ernmeut, through It's lighthouse board, | has utilized the services of the sun and made that great lamp of heaven 1 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 faroh places. Modern magic was not slow in recognizing the fact that by the ap' plicatiou of certain well known scien' tifc 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 navlgable stream in our huge country could be much simpliGed
 The United States did not become in- terested in the ocetylene light and its automatically generating gas buoy until about the year 1906 and did not adopt 1t until I0uS Then the engineers of the lighthouse board devised some wonderful improvements, among them the utilization of the sun.
 The self lighting and self eNtinguish- ing acetyIeue 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 helCOns is dissolved acetyIeue. which Is stored under pres sure in steel cylinders One of these cylinders can be charged with enough gas to last a small beacon three years. Usually. however in the case ot float. ing buoyS. a six months supply is all that is necessary, as such buoys are overhaulcd and painted twice a year. Knowing the size of the flame and its hourly consumption of gas, it is very easy to compute how long a cylinderful will last and how often it will need Co be visited. That Is an the care the light win 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 interceptlug body. Sunlight upon dark surfaces is converted Into heat, and heat produces expansion. This expan- sion Is especially percepdble tn certain metals.
 In carefully sealed and substantial ly mounted glass jar nearly a foot high and about one-fOurth that in dt- ameter a thick black rod is placed per pendlcularly through the center. It 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 ab- sorbiug lt 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 sitiye to light and heat As the sun appears and the atmosphere grows warmer in the morning this rod length. ems. It pushes down into the metal chamber in which the glass jar rests and touches the end of a lever lt presses down on this lever, which is controlled by a spring and cuts of the flow of the gas to the lamp.
 When the sun disappears from view in the evening and the temperature of the air falls the process is reversed. The rod contracts and releases its pres sure on the lever, allowing the gas to flow upward Co the lamp. The gas Is iguited by a little pilot flame that is never extinguished. Thus the beacon is lighted at the proper time and is put out when 1t is no longer needed, all though along desolate coasts 1t may never gladden. the human eye for months at time.
 The engineers of the lighthouse board say that the precision of this device is almost incredible. It can be used with equal certainty In equatorial heat and in polar cold, for 1t responds with the utmost accuracy to small variations In temperature It is used on lonely is- lands in the Pacific. There are nearly hundred of these sun valve beacons In Alaska. In summer they are aids to navigation, and in winter they guide l the travellers on dog sledges over the