L. MECHANICS AND ENGINEERING. 461 



eighths of an inch square ; they are regulated by an auto- 

 matic apparatus, and consume at the rate of four inches per 

 night for each lamp. The lenses are about the same size as 

 ordinary third-order lenses. 9 i>, March 6, 1875, 55. 



THE USE OF GAS FOE LIGHT-HOUSES. 



The great advantage of employing gas for light-house pur- 

 poses is stated to consist in the fact that, by a very simple 

 arrangement, the number of burners and the brilliancy of the 

 flame can be increased from its ordinary to an extraordinary 

 brightness, such as to provide for its visibility in all kinds of 

 thick weather, except, of course, that condition of fog which 

 no light, not even the sunlight, can penetrate. In a fixed- 

 light apparatus, of any size, there is no occasion to alter the 

 existino: lenses if we wish to introduce the use of cjas instead 

 of oil; but in some lamps it may be necessary to provide for 

 additional ventilation. The cost of gas-light is said to be 

 less than that of oil, while the photometric value of the flame 

 of gas is largely superior to that of any kind of oil. When the 

 "fog-power" of the gas-light is turned on, the cost of the gas 

 per hour is greater; but taking the average of a year's con- 

 sumption, at several light-houses, it appears that there is an 

 actual saving of about $300 per year by the use of gas. A 

 very simple apparatus eflects an automatic intermission in 

 the light, which not only saves somewhat in the consumption 

 of 2:as, but acts as a means of distino-uishingj one liQ:ht-house 

 from another, precisely as is at present brought about by the 

 introduction of the flashing system. A gas-light of the first 

 order, employing Mr. Wigham's gas-burners of 108 jets, would, 

 if fixed, be equal to 70,000 standard candles ; but, if revolv- 

 ing, be equal to 873,000 candles. ElUott''s European Light- 

 house System . 



THE ELECTRIC LIGHT FOR SIGNALING. 



A series of experiments has lately been made at the cele- 

 brated Siemens-Halske Telegraph Works, in Berlin, with the 

 object of testing the adaptability of the electric light for sig- 

 naling purposes. The apparatus in question, which was op- 

 erated from the roof of the factory, to the great astonishment 

 of the populace, gave a light so powerful that ordinary writ- 

 ing could be read by its illumination at the distance of a 



