The oil employed in the lighthouses of Great Britain, Ireland, and France is the colza, which has of late years entirely superseded spermaceti oil, as producing an equal quantity of light at little more than half the expense. The electric light has, however, been proposed as a more powerful method of illumination. One system, in which the light is produced between carbon points by the revolution of magnets fixed on wheels, worked by a steam-engine, was tried with much success by Professor Holmes at the South Foreland; and is still, we believe, in use at Dungeness, as it is, in France, at the two lighthouses of La Hève. In the latter case, the mechanism producing the currents is composed of two steam-engines, each with a five-horse power, and of four electro-magnetic machines of six discs, composed each of sixteen bobbins. It is placed in a boat, adapted for the purpose, at an equal distance from the two towers. Under ordinary atmospheric conditions, a single steam-engine is kept in motion, communicating with a magneto-electric machine for each lighthouse. During fogs and mists, both engines are in activity, and each lighthouse receives the currents of two magneto-electric batteries, which are then associated. [Illustration: ELECTRIC APPARATUS FOR A FIXED LIGHT.] Both lighthouses are supplied with two lenticular apparatus, placed one above another in the same lantern. The regulators of the progress of the carbons were invented by M. Serrin, whose object has been to augment their sensibility, and, consequently, the regularity of the light; in which respect, now-a-days, little is left to be desired. The mean intensity of the light produced by a machine of six discs is computed as equal to 200 Carcel burners. The intensity of the cone of light emanating from the lenticular apparatus, when illuminated in this manner, rises to 5000 burners.