The Sun.
London, England, 1863-03-19 00:00:00

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'UNITED SERVICE INSTIT.

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E~i.

At a meeting of the members of the
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vice Institution on 'lll4day evening,
Mr. Findlay, was tread, " On Lighthou*,"
which he explained and commented on the diffe-
rent methods that have been contrived for concen-
trating the light, enticed particularly the ap-
plication of the electric light to lighthouse pur-
poses. The paper, which was read by Admiral
Collinson, was very elaborate, and considered sepa-
rately the construction of lighthouses, the ap-
pliances for concentrating and directing the light,
and the character of the light employed. With
respect to the construction, it was stated, and
illustrated by drawinge and by ft model, that
the recently adopt ed method of dovetailing the blocks
of stone perpendicularly as well as horizontally ren-
ders them when cemented as substantial as if the
structure were one solid'rriass of granite. Some idea
..may be formed of the force to which these structures
are exposed, when it is stated :hat during same re-
cent experiments at the Skerries JightlionF, the
waves struck ti.e buiiding*irh a ler ec of upwardsi
of 2,(d 01b. on the square ;oat. Tire chief portion of
the paper was occupied with expitnations and exa-
minations of the comparative merits of the plans
contrived for concentrating the rays *tight, so as
to prevent them from being uselessly dissipated,
and to throw them in a horizontal direction alone.
A great variety of lenses and of reflectors were ex-
hibited, which brilliantly illuminated the lecture-
room, and threw a dazzling light on all the objects
to which they were successively directed. The ca-
toptrical method of concentrating the light, by the
adaptation of lenses, has been usually considered
superior to the reflection of the light from paraboli-
cal reflectors, but in Mr. Findlay's opinion reflectors
answer the purpose better, as they do not obstruct
the rays. The combination of the two principles of
reflection and refraction, seems, however, to have
produced effects superior to either when used singly.
In considering the kind of light that can be seen at
the greatest distance, and which possesses the most
penetrating power, Mr. Findlay noticed particularly
the electric light, which has been applied at Dun-
geness lighthouse for two years with great success;
and to show the superiority of its illuminating
power it was exhibited behind a lighthouse lens
which had been previously used for concentrating
the rays of a large argand lamp with concentric
wicks. The splendour of the lamp, which was
beautifully iridescent, was quite overpowering, and
it could only be looked at when reflected from a
screen. This practical application of the electric
light was contrived by Professor Holmes, who
showed the arrangement for maintaining and
preserving it steadi y at the recent Exhibition,
when the electrical power was excited by a mag-
neto-electrical machine of great size. Professor
Holmes, who was present on this occasion, was
called on to explain the principle of his invention.
With the electric lamp before him, he pointed out
the mechanical contrivances he had applied for the
purpose of keeping the carbon points at the requi-
site distance apart, and he showed how readily the
light could be regulated and be maintained in cora-
stant action. The cylinders of carbon employed last
about three hours, and there is an arrangement at
Dungeness for renewing them without any discon-
tinuance of the light by bringing another lamp in-
stantly into action. He mentioned many instances
of the penetrating power of the light during fogs,
when no other lights could be seen, to show the
great value of the electric light when applied to
give signals at sea during foggy weather. The
coloured rays seen in the lecture-room are not, he
said, perceptible at sea, when mingled with the
other rays of light, excepting when observed
through a telescope, and then the cause of them is
beautifully apparent, and they cannot be mistaken
for a coloured light. As an instance of the pene-
trating power of the electric rays, it was stated
that on the night of the illumination, at a time wnen
the fog was so dense that to a spectator on Primrose
Hill there was complete darkness over London, the
glimmer of the electric light on the Monument could
be distinguished.
Th, nks having been Toted to Mr. Findlay and to
Professor Holmes, the meeting adjourned.