112 MARINE UGHTING EQUIPMENT OF THE PANAMA CANAL. 



device is used with the greatest success. Its construction and operation 

 are based on the well known physical law, that a body with a light absorbing 

 surface attains a higher temperature and consequently expands more than a 

 similar body with a light reflecting surface, when both are exposed to the 

 same light. Plate 57 shows a vertical section through the sunvalve. The 

 number i indicates a central copper rod, the surface of which is coated with 

 lamp-black to give it the property of absorbing light to the greatest possible 

 degree; 2 indicates a smaller rod, of which there are three arranged sym- 

 metrically around the central rod i . 



These three rods are also made of copper, but have surfaces of polished 

 gold which causes them to reflect light to the greatest possible degree. The 

 rods 19 pass loosely through plate 20, and serve only as a support for the 

 dial plate 16. The rods 2 are held in position between the valve-body 22 

 and the plate 20 by means of the spring 2 1 . The lower end of the central 

 rod I bears on the valve lever 6 at a point between the fulcrum 23 and the 

 valve seat 7. 



When light is withdrawn from the apparatus, the rod i contracts and 

 the valve 7 is opened by means of a spring 8, thus allowing the gas flowing 

 into the valve chamber 22 through pipe 9 to pass out again through pipe 10 

 to the burner ; but when light falls upon the apparatus it is absorbed by the 

 blackened central rod i, and transformed into heat which causes the rod 

 to expand, and forces the valve lever 6 down upon the valve seat 7, thus 

 shutting off the flow of gas to the burner. The rod i is arranged so that 

 it can only expand downward. 



The light which falls on the gold plated rods 2 is reflected out again 

 without having any influence on them. 



The upper end of the rod i bears on an adjusting screw 14, which is 

 secured to the dial plate 16. By turning this screw up or down the position 

 of the lever 6 can be adjusted to give the sunvalve any desired degree of 

 sensitiveness. The position or adjustment of the screw is indicated on the 

 dial plate by the pointer 15. . 



All the rods and the upper parts of the sunvalve are securely protected 

 by the glass cylinder 18. 



Within little more than a year the faith and enterprise of the American 

 people will have been rewarded; through the wonderful skill and courage 

 of their army engineers, the great connecting link between the two oceans 

 will have been completed, the lights will have been established, and lighted ; 

 in daylight or in darkness, with equal security, the ships of the nations will 

 pass through and a new chapter will have been written in the world's history. 



