70 
LIGHTHOUSE ILLUMINATION BY MAGNETO-ELECTRICITY. 
five miles ; then, if the Electric 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 Elec¬ 
tric 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 power, though the telescope 
showed that the alteration in the lantern had taken place at the right time.” M. Rey- 
naud estimates the usual intensity of the light at from 180 to 190 standard Carcel bur¬ 
ners. 
This superiority of brightness is of practical service only in thick weather, for if the 
air be clear an ordinary first-class light under the old system answers every purpose of the 
mariner, and in fog no light is of any avail; but it scarcely requires demonstration that 
in certain intermediate states of the atmosphere, the brighter light will penetrate the 
haze, rain, or snow to a distance at v/hich the other is perfectly invisible. There is no¬ 
thing in the nature of the rays emitted to prevent its doing so, for when submitted to 
spectral analysis, the Electric light is found to contain every ray that the oil-flame does, 
and others besides. The returns of neighbouring lighthouse keepers, and of the masters 
of two of the lightships at the Goodwin Sands, during the experiment at the South Fore¬ 
land, show this to be actually the case, and similar testimony is borne by the masters 
of passing vessels, the commanders of the Channel Steam Packets, and the pilots who 
frequent the neighbouring seas. 
The peculiar bluish colour of the light as seen from a distance is another advantage, 
by distinguishing it from ships’ lights, or lamps on shore; and practically this is a great 
object. Of course, it may be made red or green, or any other tint, by coloured glasses; 
indeed, it is peculiarly adapted for such a purpose. As the light can be interrupted and 
immediately rekindled with full intensity at pleasure, this light offers facilities for signal¬ 
ing which no other does. Each lighthouse might be made to repeat its own number all 
night long, if that were thought desirable. Another advantage is well stated in the 
words of Professor Faraday :—“ In cases where the light is from lamp-flames fed by oil, 
no increase of light at or near the focus or foci of the apparatus is possible beyond a 
certain degree, because of the size of the flames; but in the Electric lamp, any amount 
of the light may be accumulated at the focus, and sent abroad at, of course, an increased 
expense. In consequence of the evolution of the light in so limited a focal space, it 
may be directed seaward, diverging either more or less, or in a vertical or horizontal di¬ 
rection at pleasure, with the utmost facility. The enormous shadow under the light, pro¬ 
duced by the oil-flame burner, which absorbs and renders useless the descending rays to 
a very large extent, does not occur in the Magneto-electric lamp ; all the light proceed¬ 
ing in that direction is turned to account. The optical part of the arrangement, whether 
dioptric or reflecting, might be very small in comparison with those in use and, in¬ 
deed, it is so at Dungeness. As there is always an extra steam-engine and machinery 
on the premises, and ready for work, the power, and the consequent light between the 
charcoal points, might at any time be doubled, if the state of the atmosphere seemed to 
require it. 
It has already been remarked that in fog no light, however powerful, is of much avail, 
and public attention is now being directed to the necessity of improving our fog signals. 
It has been well observed in M. Reynaud’s Report, “ During foggy weather the supple¬ 
mentary steam-engine might be employed in playing sonorous instruments, which would 
carry sound to a much greater distance than the bells to which we have recourse at pre¬ 
sent.” 
Against the advantages attending the use of this Electric light must be set the greater 
complexity of the instrument, and the consequent greater chance of derangement, or 
rather the necessity of providing lighthouse-keepers of a superior order, and an engineer 
to inspect the machinery and keep it in repair. This demand for superior workmen is a 
difficulty we generally have to encounter in perfecting our engines either of peace or 
war. 
The relative expense of the Magneto-electric light and the Fresnel lamp is a consi¬ 
deration that must not be overlooked, though it should not be allowed too much weight 
when we are dealing with the safety of valuable cargoes and priceless human lives. The 
original outlay in machinery for the Electric light is very large, but there must be set 
