The Sun.
London, England, 1865-10-05 00:00:00

Our Lights and Lighthouses.*

s-, ---

At a very remote period, when the early mariners of
the world first ventured to extend their sea-voages beyond
the few hours of daylight, or of moonlit nights, the want
must have been felt of warning and guiding lights, and the
more especially as those primitive voyagers, who were the
first pioneers of commerce, must have perpetually "hugged"
the shore, their chief fear being that they should be carried
away by an " off-shore" wind into the great unknown
region of waters extending they knew not whither.
The buildings specially constructed for the exhibition of
beacon lights, of which there is historic record, were of
very ancient date, but far, very far beyond that age must
we carry our mental vision in imagining the period
when the first signal-fires were piled on the hill-side, or
rocky point, or overhanging cliff, to guide the absent
mariner safely to his home again.
Interesting, however, as it may be, as a subject for re-
flection and conjecture, to trace the gradual development
of huthan prognss in all matters, from the rude and simple
state of a remote and ignorant barbarism to the compara-
tively complex and refined civilization of the present time,
we have now ratherto do with the practically useful than
with the sentimental; we shall therefore proceed at once
to describe the successive improvements in the great sea-
lights of a later age.

There can be no doubt that all the earlier lights were
simply fires of wood. The Tour do Corduan, when com-
pleted in 1610, was provided with an iron chauffer or cage
in which faggots of wood were burned ; and in our own
country, where coal is more abundant than in most others,
open coal fires were sometimes adopted, a light, of which
description was actually in use at the Isle of May, on the
coast of Scotland, from the time of the erection of its light
tower, in 1636, until so late as the year 1816, when a new
tower was built, and was provided with oil lamps and re-
flectors. No less than 400 tons of coal were latterly burnt
each year in maintaining this light.
The disadvantages of this primitive mode of illumina-
tion were manifold. The -degree of intensity, size, and
even colour of the light must have been very variable, the
distance at which it could be seen being equally so ; it did
not admit of any distinctive marks by which one light
could be distinguished from another ; the quantity of fire
consumed was enormous, and its supply must, in propor-
tion, have involved great labour and expense ; while the
waste of light was likewise great, since it shone in all
directions, towards the land as well as towards the sea, and
upwards to the sky. It is, however, recorded of the wood
and coal fires as an advantage, that, in wet and foggy
weather, their reflection was distinguishable high up in
the air when they were not themselves visible.

The next change appears to have been first adopted at
the Eddystone, at which, from its isolated position, being
several miles from the land, it would have been very diffi-
cult to maintain a sufficient supply of fuel in the winter
months. Its illuminator was accordingly composed of 24
wax candles, surrounded by a glass lantern, but without
reflectors, or any other artificial means of increasing or
concentrating the light; and insignificant as it must have
been, compared with the splendid lights of the present day,
the plan was yet a considerable step in advance of the open
fires.

The next great improvement in sea-coast lights was the
adoption of reflectors, which, like many other improve-
ments in the various deparments of art, science, and manu-
factures, appears to have been the immediate result of ac-
cident rather than of deliberate design and forethought.
Before, however, proceeding to describe the successive
advances in the science of pharology, or the branch of
"Optical Engineering" as it is called, which applies to sea-
coast illumination, it will be desirable, for the information
of unscientific readers, that, without going deeply into
optical details, we should briefly explain the principles on
which science is made available to produce such truly
valuable practical results.

Rays of light travel through space in all directions, and
in straight lines, unless diverted therefrom by reflection
from the surface of an opaque body, such as silvered glass
or polished metal, or by refraction in passing through trans-
parent bodies, as glass or water. If then two diverging
rays of light, or bundles of rays, can be thrown, either by
reflection or refraction, on one point, thus occupying the
space of one ray or bundle of rays, the intensity or
brightness of the light on that point will be double : if 20
doubled ; if twenty rays are thus made to converge into
the space of one ray, the brilliancy at the point of conver-
gence or focus will be increased twentyfold. A familiar
instance of this principle, by refraction, exists in the com-
mon glass lens, vulgarly called a "burning glass," which,
by throwing a large number of rays of light on one point,
produces an intense light and heat, capable of exploding
gunpowder and igniting inflammable bodies. In the same
manner, the shape of a mirror or reflector may be so
arranged as to collect the rays of light emitted on one
side of a luminous body, and to throw them forward, so
that they shall converge in a point, or series of points,
on the opposite side, and thus being added to the direct
rays, increase the intensity of the light on that side.
A concave mirror, the curve of which is a parabola, is
found to be the necessary form to effect the object in view,
and a series of such rcflecLors, attached tn lamps_ suitably
adjUsted:thus collect the useless rays.of light from above,
below, and behind, and throw them forward in a horizontal
direction. As stated above, this system, which has been
denominated the catoptric or reflector system, from the
G-reek word mrrpov, a " mirror," was the first that
was employed in the improvement of beacon lights. It is
essentially the English system, both from its having been
originated and been longer retained here than in other
countries. The credit of first introducing it has been
claimed both by England and France. Undoubtedly,
however, the earliest application of reflectors was made in
England, whilst to France belongs the honour of very
greatly improving them.

Somewheie between the year 1763 and 1767, Mr. William
Hutchison, the dockmaster at Liverpool, first applied a
parabolic reflector to his flat-wicked lamps. The idea is
stated to have thus originated. A convivial company of
scientific men met at Liverpool, when one of the company
present wagered that he would read a book by the light of
a farthing candle, at a distance of 200 feet from it. The
wager was won by means of a wooden bowl, lined with
putty, in which facets of looking-glass were embedded,
forming a reflector. Hutchinson was present, and
seizing the idea, utilised it for his light-
houses. His reflectors were formed of tin plates,
or of wood lined with looking-glass, the largest
15 feet in diameter with 6 feet focus, being placed behind
a " spreading burner mouthpiece" 14 inches broad. The
Ridstone, Hoy lake, and Leasowe lighthouses were thus
illuminated, and they were undoubtedly excellent light for
the period.

In the year 1786, the Northern Lights Board fitted re-
flectors and lamps of a similar description, at the Isle of
May and °umbrae Isle lighthouses on the Friths of Forth
and Clyde. These were said to have been the invention
of Mr. Thomas Smith, the engineer to the board ; but whe-
ther or not he was aware of similar reflectors having been
adopted elsewhere is not known.

On the other hand, in France, a M. Teulere, a member
of the Royal Corps of Engineers of Bridges and Roads in
that country, is said to have first proposed the use of para-
bolic reflectors ; and the celebrated Corduan light-tower
was illuminated in that manner about the year 1780, by
M. Lenoir, under the direction of the Chevalier Borda.
The reflectors were made of sheet copper, plated with
silver, and the lamp then just invented by 11. Argand, of
Geneva, since known as the Argand lamp, was adopted.
These greatimprovements then became general in other
countries, and at once advanced the system of lighthouse
illumination into a science. The reflectors of the present
day are made precisely in the same manner as M. Lenoir's,
of copper thickly plated with silver, very highly polished,
and, like his, lit by Argand burners, having a cylindrical
flame of about one inch in diameter. The form of those
now in use is that calculated by Captain Huddart, an
Elder Brother of the Trinity House, in 4791. They are
very durable, many of the reflectors still used remaining
unimpaired after 30 and 40 years' continued service.

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The size adopted by the Trinity House is 21 inches dia-
meter for lighthouses, their sectional area being 346.3
square inches, and 12 inches diameter for light vessels,
with an area of 113 square inches. Some reflectors are said
to multiply the brilliancy of t-4, light as much as 450 times.
Catoptric lights are capable of nine distinct variations, viz.,
fixed revolving white, revolving red and white, revolving
red with two whites, revolving white with two reds, flash-
ing, intermittent, double fixed, and double revolving. The
first exhibits a steady and uniform appearance. The re-
flectors used for it are of smaller dimensions than those
employed in revolving lights, and which is necessary in
order to allow of their being ranged round a circular iron
frame, with their axes inclined at such angles as to enable
them to illuminate every part of the horizon. The re-
volving light is produced by the revolution of a frame with
three or four sides, having reflectors of a large size
grouped on each side, with their axes parallel ; and as the
revolution exhibits a light gradually increasing to full
strength, and in the same gradual manner decreasing to
total darkness, its appearance is extremely well marked.
Eighteen, twenty, and even thirty reflectors are thus ar-
ranged on the faces of the revolving framework.
The succession of red and whit) lights is caused by the
revolution of a frame whose different sides present red and
white lights, and these, as already mentioned, afford three
separate
red f
alternate red and white, the suc-
cession of after one red, and the succession of
w
The flashing light is produced
t adistinctions,
tetrw oo nwhitew
h viz.,ite.
o
in the same manner as the revolving light ; but by a dif-
ferent construction of the frame and greater quickness of
the revolution, a totally different and very striking ap-
pearance is produced. The brightest and darkest periods
being but momentary, the light is ch9„racterised by a rapid
succession of bright flashes, whence Irderives its name.
The intermittent light is distinguished by bursting sud-
denly into view, and continuing steady for a short time,
after which it is suddenly eclipsed for many seconds, ordi-
narily in English lights for about half a minute. Its pecu-
liar and striking appearance is effected by the perpendicu-
lar motion of circular shades in front of the reflectors, by
which the light is alternately concealed and displayed.
The double lights, which are commonly only used where