The Birmingham age-herald., 1912-11-03

verted into heat and heat produces eX- pansion This expansion is especially per- ceptible in certain metals In a carefully sealed and substantially mounted glass jar nearly a foot high and about one fourth that in diameter thick black rod is placed perpendicularly through the center. It is supported by three slen- derer 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 de- gree The supporting rods reflect light without absorbing it and do not ex- pand or contract to the same extent as the largest rod
 The thick black piece of copper in the center of the jar is extremely sensitive to light and heat. As the sun appears and the atmosphere grows warmer in the morning this rod lengthens 1t pushes down into the metal chamber in which the glass jar rests and touches the end of a lever. It presses down on this lever. which is controlled by a spring, and cuts off the flow fthe gas to the lamp.
 When the sundisappears from view in the evening and the temperature of the air falls the proces sis reversed. The rod contracts and releases it's pressure on the lever. allowing the gas to flow upward to the lamp. The gas is ignited
 
 tinguished. Thus the beacon is lighted at the proper time and is put out when it is no longer needed, although along desolate coasts it may never gladden. the human eye for months at a 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 it responds with the ut most accuracy to small variations in temperature. It is used on lonely islands in the Pacific. There are nearly 100 of these sun valve beacons in Alaska. In summer they are aids to navigation and in winter they guide the travellers on dog sledges over the frozen waters.
 The lighthouse board, which has charge of the construction and maintenance of lighthouses, light vessels, lighthouse de- pots. beacons, fog signals, buoys and their appendages, and all the property that appertains to them, Is now one of the divisions of the department of com- merce and labor. Before the creation of that department 1t was a distinct bu- reau of the treasury department. It's practical supervision Is still in the hands of navy and army officers specially de- tailed to these duties by the secretaries of the nav wand war. Army men of the engineer corps look after the construc- tion of the important buildings like those along the seacoast and the Great Lakes. This dovetails with the supervision by the war department of the river and harbor works. Naval officers of the prop CT rank and experience are assigned as inspectors of the 19 districts and in the inland service especially they are sub stantially the executive heads. Their word is law. The position of chairman of the lighthouse board at Washington is a post of great dignity and import ance and always goes to the navy. Ad- mirals Dewey, Schley. Walker, Evans. and other sailors of renown' have held this post.
 The lighthouse service of the United States costs about $5.000,000 a year. The greater part of this sum is used in car ing for the lighting of the coasts.