1864. | Guavstong on Lighthouse Illuminations. 73 
into one stream, and by a special piece of apparatus called a Com- 
mutator the alternate positive and negative currents are all brought 
into one direction. The whole power is then conveyed by a thick 
wire from the engine-house to the lighthouse tower, and up into the 
centre of the illuminating apparatus. There it passes between two 
charcoal points, producing thus a most brilliant and continuous spark. 
The “Lamp,” or ‘‘ Regulator,” is so contrived that by means of a 
balance arrangement and a magnet, round which the wire coils, the 
charcoal points are kept always at a proper distance apart. 
At sunset the machine is started, making about 100 revolutions 
per minute ; and the attendant has only to draw two bolts in the lamp 
when the power thus spun in the engine-room bursts into light of 
full intensity. It now requires little or no thought for three hours 
and a half, when the charcoal points being consumed the lamp must 
be changed, and this is done without extinguishing the light, for it is 
the kindling of the second lamp that puts out the first. There are 
always several lamps ready at Dungeness in case of accident, and 
everything is kept in duplicate. 
The French machine is composed of 56 magnets distributed in 
7 vertical equidistant planes, upon the angles of an octagonal prism. 
The maximum of intensity is obtained when the machine turns 350 
or 400 times per minute, and the direction of the current is then 
reversed nearly 6,000 times per minute. There is no Commutator 
employed, and the alternate currents are not brought into one. 
Merits and Demerits.—In favour of the Electric Apparatus, it 
may be stated without any fear of contradiction that the light is vastly 
more intense than that produced from the most powerful oil-lamp, or 
any practicable number of argand burners. In truth that now shining 
at Dungeness is the most brilliant light in existence. The following 
statement will illustrate this. Professor Faraday says of it, when at the 
South Foreland, ‘“ During the daytime I compared the intensity of the 
light with that of the sun, that is, it was placed before and by the side 
of the sun, and both looked at through dark glasses; its light was as 
bright as that of the sun, but the sun was not at its brightest.” No 
other light in existence would have stood that test. Again, he 
describes an experiment at Dungeness :—‘ Arrangements were made 
on shore, by which observations could be made at sea about five miles 
off on the relative light of the Electric lamp, and the metallic reflectors 
with their argand oil lamps—|the light formerly used|—for either 
could be shown alone, or both together. .... The combined effect 
was a glorious light up to the five miles; then, if the Electrie light 
was extinguished, there was a great falling off in the effect; though, 
after a few moments’ rest to the eye, it was seen that the oil-lamps 
and reflectors were in their good and proper state. On the other 
hand, when the Electric light was restored, the glory rose to its first 
high condition. Then, whilst both were in action, the reflectors were 
shaded, and the Electric light left alone; but the naked eye could 
see no sensible diminution ; nor when the reflectors were returned into 
effectual use, could it see any sensible addition to the whole light 
