1872.] Iilununation of Beacons and Buoys. 23 
Thus the light seen by the seaman is merely a reflection of 
that on shore, the parallel rays of the shore-light being 
undistinguishable at the distance from which the apparent 
or reflected light is seen. One of these apparatus is erected 
at the Bay of Stornoway, a well-known anchorage in the 
Island of Lewis, the reflecting beacon being erected on 
Arnish point, a sunken reef on the south side of the 
entrance. This beacon is distant 530 feet from the real 
lighthouse, and consists of a truncated cone of cast-iron 
bearing the reflectors, which are exactly on a level with the 
window whence the light is projected. The beacon thus 
directly marking the spot to be avoided is only accessible at 
the low water of spring tides, and this is, therefore, the only 
kind of light available. But there are situations in which a 
beacon cannot, owing to a great depth of water, be erected, 
and it becomes necessary to ascertain whether a buoy 
could be employed. From experiments made on different 
parts of the coast, Mr. T. Stevenson finds the application 
would be perfectly practicable. The difficulty to be sur- 
mounted is the swinging of the buoy at its moorings; this, 
however, can be compensated by causing the rays from the 
shore to subtend a sufficient space to always include the 
reflectors. 
The apparent light is such a marked improvement upon 
the dipping light, which merely illuminates the sea covering 
the dangerous spot, at a very small additional expense, that 
there can be no doubt of its substitution. 
The third method of illumination, not as yet fully deve- 
loped is, however, of paramount importance, as providing 
light for those situations where the apparent light is inap- 
plicable. Faraday’s discovery of the magneto-electric 
spark was first adapted to lighthouse illumination by Pro- 
fessor Holmes, and employed by the Trinity House in 1858, 
at the South Foreland Lighthouse. In 1862 this apparatus 
was placed at Dungeness, and here it has continued to give 
out its light nightly, having been extinguished on only one 
occasion, and then but for four or five minutes. Professor 
Holmes’s machine consists of a number of powerful 
magnets, fixed into an o¢tagonal frame. Bobbins or rods of 
soft iron, around which are coiled helices of silk-covered 
copper wire, are caused to rotate before the poles of the 
magnets, the result of this rotation manifesting itself as 
powerful electric currents in alternate directions. These 
currents, brought to one direction by means of a commu- 
tator, are conveyed from the machinery-room to two carbon 
points fixed in the lantern of the lighthouse. The carbons 
