460 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



is at a high pressure, and is drawn off at intervals, there is a 

 constant tendency to foam and throw out water with the 

 steam. To counteract this, a horizontal tubular boiler, like 

 those used in locomotives, is recommended by him. The 

 steam-dome must be very large, and surmounted by a steam- 

 pipe twelve inches in diameter. The steam should be drawn 

 off at a point ten feet above the water-level in the boiler. 

 The diameter of the boiler whistle should be two thirds of 

 its length, and the vertical distance of its lower edge above 

 the coping for a steam pressure of fifty pounds should be from 

 one third to one fourth of the diameter. EllioWs European 

 Light-house System^ p. 25. 



THE ELECTRIC LIGHT-HOUSE AT SOUTH FORELAND. 



In the light-house at South Foreland the electric light is 

 employed, and the electric current is generated by means of 

 large magneto-electric machines, which are driven by belting 

 connected wdth a steam-engine. Each machine is composed 

 of 96 helices, mounted upon six gun-metal wheels, each of 

 which carries 16 helices. Between these wheels are placed 

 the magnets, eight in each division, 40 of which are com- 

 posed of six layers or leaves riveted together, while the 16 

 end ones have but three leaves each. The masrnets, which 

 are mounted in frames, are stationary, while the helices re- 

 volve at the rate of 400 revolutions per minute. The power 

 absorbed by the electric machine alone, including friction, is 

 four indicated horse-power. The power of a magneto-electric 

 machine is according to the gross attractive jjower of its 

 masfuets, each ma2:net havino: a certain liftimx or attractive 

 power expressed in pounds. In the machines at South Fore- 

 land each of the six-plate magnets will lift 108 pounds, and 

 each of the three-plate magnets 54 pounds, making the at- 

 tractive power of the magnets in one machine to be 5184 

 pounds. The proportion of the lifting power to the weight 

 of a magnet is a good indication of its value, and, generally 

 speaking, a magnet which will lift two and a half times its 

 own weight is a good one. Each six-plate magnet at South 

 Foreland has a weight of 43^ pounds, or tAvo fifths of 108 

 pounds. The machines are connected by underground cables 

 with the electric lamps placed in the lenses of the tower. 

 The carbons used in the lamps are ten inches long by three 



