150 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



light in foggy weather, and more notably as the fog thick- 

 ens. In general, it is found that if the electric light has an 

 intensity two and a half times greater than the oil-light, it 

 will penetrate fog as well as the latter. The expense of the 

 powerful electric light at La Have is about one seventh 

 greater than that of the decidedly inferior oil-lights. Gen- 

 eral testimony seems to be in favor of the introduction of 

 the magneto-electric light at all important stations, and botli 

 the English and French are extending its application. 

 Elliot'' s European Light-house System, p. 248. 



THE ROMAN PHAROS IN DOVER CASTLE. 



There is still standing within the walls of the castle at 

 Dover, England, an old Roman pharos. The antiquity of 

 this light-house, which has probably not been used as such 

 since the Norman conquest, no doubt exceeds that of any 

 light-house in Great Britain, it having been built, as is sup- 

 posed, about A.D. 44. Upon it burned for many centuries 

 great fires of wood or coal, the modern system of lamps and 

 reflectors having superseded coal fires during the last cent- 

 ury. This pharos, like the one at Boulogne, is built of bricks 

 in color and shape like those found elsewhere in the Roman 

 structures of Great Britain. They are of a light red color, 

 about fourteen inches long, and not more than an inch and 

 a half thick. The mortar joints are of nearly the same thick- 

 ness. The preservation of this famous relic is doubtless due 

 to the fact that some centuries ago the tower was turned 



Cj 



into a belfry, and was surrounded by walls of stone. The 

 latter are now nearly destroyed by time, and the old re- 

 maining work is again exposed. Elliot's European Light- 

 house System, p. 73. 



THE POWER OF THE ELECTRIC LIGHT. 



The most powerful artificial light at present in existence 

 is that employed for the great light-house at Souter Point, 

 on the coast of England, near the mouth of the Tyne. 



On both banks of this river there is an immense number 

 of manufactories of all kinds, the smoke from which, under 

 the influence of the west wind, seriously obstructs the ap- 

 proaches from the sea. Fogs at this part of the coast are 

 also frequent; and the problem of light-house illumination 



