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"All down the lonely coast of Lyonesse, Each with a beacon star upon his head, And with a wild sea-light about his feet, He saw them, headland after headland, flame

Far on into the rich heart of the West."

Yet we have no knowledge of the method of illumination adopted by the ancients, and the whole of the present history will be confined almost within the narrow limits of a century. The materials of the sketch will be drawn from Alan Stevenson's Treatise on Lighthouses, and from various sources of information which were open to the writer when serving as a member of the Royal Commission on Lights, Buoys, and Beacons, under the presidency of Admiral Hamilton, whose report was laid before parliament last spring.

Many lighthouses, still standing, have witnessed the whole of the important changes that have taken place in the art of illumination. Thus the beautiful Tour de Corduan, at the mouth of the Gironde, first exhibited a light obtained by burning billets of oak in a chauffer; then coal was substituted for wood; afterwards a large tinned reflector was placed above this fire to throw down the light which had previously been wasted on the sky. Next oil lamps and paraboloidal reflectors were employed; and, lastly, the tower was crowned with the first apparatus of lenses that ever gave to the mariner the light of a four-wicked lamp.

It must not be supposed that these various changes of system took place simultaneously in different countries, or even in different parts of our own country. The fact is, that the lighting of the shores of the British Isles has been undertaken by a large number of different corporations, and, till recently, by some private individuals; and some of these have been naturally more conservative than others-the large bodies generally, but not always, taking the lead in improvements. These bodies

are the Trinity House in England, the Commissioners for Northern Lights in Scotland, and the Ballast Board in Ireland, which have under their juris

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diction nearly all the great shore lights in the respective countries. The two last are subject, in some particulars, to the first; the three have a limited power over the harbour lights, which belong to perhaps a hundred municipal authorities; while the Board of Trade has a not well defined "control of the purse' over them all. Should the recommendations of the Royal Commission be adopted, the system of government will be greatly simplified; yet, even then, we can hardly expect that new improvements will be extended at once throughout the whole lighthouse service of the country—for new apparatus is costly, and indeed different plans of illumination suit different localities. But in a historical paper we have only to deal with things as they were and are.

There is a peculiarity about the history of lighthouse illumination which may perhaps be best illustrated by comparing it with the geological history of our earth. In that we are accustomed to recognise various epochs-one age of luxuriant vegetation, another of huge saurians, another of mammalia. Yet we know that these ages are not separated by sharp lines of demarcation ; we cannot say when in the progress of time the little rodent first made its appearance; and, though the trilobite and the pterodactyle have long been displaced, the pentacrinite and the iguana still survive in limited regions, the relics of a former age. Just in a similar manner we can point to certain epochs in lighthouse illumination. It is difficult to define their commencement; the day of their glory is clear enough, their decadence is slow; and, though the coal-fire has become extinct, specimens of antiquated lamps and primeval reflectors are still to be found in remote localities.

I proceed to give an account of these various epochs.

Coal-fires. The earliest records are of open coal-fires which were kept burning on the top of beacon towers throughout the darkness of night. Of course these had many disadvantages; not the least

of which was that, if the wind were blowing hard from the sea, it blew the flames to the landward side of the fire, and little light was displayed to the mariner when seeking to avoid a lee shore, in the hour of his greatest need.

At the lighthouse on the Isle of May a coal-fire was burnt from 1635 to 1816. Two years ago I conversed with a keeper at Harwich, who remembered the coal-fire there, and the blowing of the bellows, and the constant attendance without shelter from the weather. The last fire of this description in England was extinguished at St. Bees, in 1822.

One evil connected with this system has been entailed on us. For the sake of distinguishing one beacon from another, it was found necessary in some cases to build two towers with coal-fires near together, and even three towers-at any rate in France. And this means of distinction is actually still retained in some places, where not wanted as a leading light, although it doubles the

expense.

Candles. Candles appear to have been seldom employed as a source of light in beacons; but in the Eddystone lighthouse, on the construction of which so much ingenuity and labour were expended, twenty-four wax candles gave their feeble glimmer as late as 1811.

Oil. The use of oil as a combustible can be traced as far back as 1730; but it was very gradually that the oil lamp displaced the coal-fire. Sperm oil was generally employed. The French, however, used Colza oil, and this was found to be more economical, and not liable to be frozen in cold weather; and, after a strong recommendation by a parliamentary committee that sat in 1845, it was at once introduced into the lighthouses under the management of the Trinity Board, and more slowly into those of Scotland. The Board of Admiralty still prefers the expensive and troublesome sperm oil for the lights under its jurisdiction; while the merchants of Liverpool have a peculiar preference for olive oil.

Oil implies a lamp. Many have been the modifications which lighthouse

lamps have undergone. In the museum attached to the lighthouse establishment at Paris, there is a curious row of contrivances, from the tin lamp with a spout and a skein of cotton in it, like the old Roman form, to double wicks, and flat wicks, and argand burners, and lastly, the grand four-wicked lamp invented by Fresnel and Arago. Some of these discarded forms still linger in lights under local management. For instance, on the pier at Douglas, in the Isle of Man, "the lamp used is exactly the same as the common lamp hung in the poorest fisherman's cottage, and as old as the Italian tombs."

Oil-lamps with mirrors. It requires no profound knowledge to see that whatever light is allowed to stream from a lamp over the land, or up to the sky, is so much light wasted, and that, if it were thrown back across the surface of the sea, it would be so much gained to the mariner. The use of mirrors for this purpose early suggested itself; and it seems likely that the lights erected in 1763, at Bidstone and Hoylake near Liverpool, were furnished even then with the large reflectors which they certainly possessed not long afterwards. It was about 1783 that paraboloidal mirrors on a revolving frame were erected on the Tour de Corduan; and the example was almost immediately and extensively followed in the United Kingdom.

But the mirror has seen many changes, and has grown in cost and efficiency, if not in size. The most primitive form that showed any scientific sense was the hollow paraboloidal mould, lined with narrow strips of flat quicksilvered glass; and such reflectors are actually still in use at the pier lights at Newhaven, where an antiquated tin box serves as the lamp, and the oil-sperm oil-rises by three primitive wicks, and, for want of proper burner and chimney-glass, fills the chamber with smoke. This form was succeeded by parabolic reflectors of silvered copper, in the centres of which were argand burners, so placed that the rays which struck upon them were sent forward in straight lines towards the sea

horizon. Of course these lamps and reflectors could be multiplied on the same framework to any extent required, and the capital invention of revolving lights was then made. As each lamp sends a direct ray to a ship at sea, decreasing in intensity as the square of the distance, and, at the same time, sends a strong beam of reflected light to some portion of the horizon, it is evident that, by rotating the mirror, or the whole apparatus, this beam of light may be made to sweep round, and illuminate every portion of the horizon successively. By multiplying such mirrors, a number of beams of light may be made to sweep over the sea, like the spokes of a mighty wheel of fire. By varying the number or the velocity, different periods may be imparted to the flash. The effect of this is that a revolving light so constructed appears, from the deck of a ship at no great distance, as a permanent faint light, varied at regular intervals by a much more brilliant blaze; as the vessel goes farther away, the waxing and waning of the light is very perceptible, and at length only the bright flashes are seen. The advantages of these revolving lights are manifold. They send a ray farther than could be effected otherwise with the combustion of the same amount of oil; they catch the eye of the mariner; and they afford an easy method of distinguishing lighthouses from one another, or from common shore or ship lights.

Argand fifty years ago suggested a combination of the parabola and ellipse, and Handry a combination of the cone and parabola, as preferable for these mirrors; but the theoretical advantages of these forms do not appear to have been put to the test of actual use. Bordier Marcier invented some ingenious modifications of the parabolic mirror, which were adopted for the harbour lights of France; but they have been since discontinued, and the only place in the British Isles where I have found such an apparatus in use is Littlehampton.

The simple parabolic silvered reflector still holds its ground in the United

Kingdom. There was a time when it reigned supreme, and when England stood pre-eminent among the nations for the efficiency of the beacon-lights along her coast. Even now the silvered reflector is almost universal in the floating lights, and, though it has been driven out of half our principal lighthouses by another instrument, it is still retained in many of the best; and the multitudinous evidence recently collected places it beyond a doubt that many of our grand revolving reflector lights compare favourably with the best lights of foreign countries. Such a light is that at Beachy Head, where thirty burners, consuming 1000 gallons of oil annually, are arranged on a triangular stage, in such a way that ten reflectors at once direct a beam of ten-fold brilliancy to the same part of the ocean.

Oil lamps with lenses.-While a mirror gathers up and renders serviceable the light that radiates behind a lamp, it allows the front rays to travel at their will to the sky, or the sands at the base of the cliff, so that few reach the mariner. The idea occurred, that this might be obviated by placing a lens in front of the light; but a trial made last century, in a lighthouse at the south of England, proved a failure-partly, no doubt, on account of the thickness and badness of the glass, and also because it destroyed the efficiency of the parabolic mirror. Buffon and Condorcet showed how to make gigantic lenses without any great thickness of material, by dispensing with everything beyond what was necessary to give the right refracting surfaces. Then arose the greatest genius of lighthouse illumination, Auguste Fresnel. The French government, in 1819, finding their lighthouse system extremely imperfect, commissioned Fresnel to go to work on the subject. The idea of using lenses took firm possession of his mind; he experimented carefully and well, and in 1822 brought forward his proposition for surrounding the flame of a gigantic lamp by lenses made in many rings of crown-glass, subtending an angle of forty-five degrees. By this means he gathered about one third of

the whole light into a few sheafs of rays, which could be easily made to revolve, while the light which radiated above these lenses, was sent along the surface of the sea by a combination of lenses and mirrors. This apparatus was proposed by its inventor for the Tour de Corduan; an experiment was made with it, on the 20th August, 1822, before the Commission des Phares; it was considered successful, and the plan was adopted. But the French government did not stop here. A comprehensive scheme was proposed for improving the lighthouse system of the country, building new lighthouses, altering old ones, introducing the lenticular apparatus, and varying the appearance of the lights. And badly enough was such a general scheme wanted. The French coasts were then wretchedly lighted; for instance, there appears to have been only one French light in the Mediterranean. Sixteen others were proposed. The French side of the Channel was better supplied; yet even there great changes were loudly called for. The matter was entrusted to M. de Rossel, whose general scheme was approved by the Commission des Phares, May 20, 1825, and referred to him and Fresnel for further development; which was given to it in a report dated September 9th of the same year. This comprehensive plan was speedily carried into effect, and the lighting of the coasts of France became almost as good as it is at the present day.

The merits of the lenticular arrangement did not long remain unappreciated by other countries. The Dutch have the credit of first following the good example. The Scotch Board soon sent their engineer to study the new system; but, though constantly urged on by Sir David Brewster, who had long previously experimented on lenses, it was only on October 1st, 1835, that the first lens-light was exhibited in Great Britain, at Inchkeith, in the Firth of Forth. This was quickly followed by a change in several other Scotch lights, and by the Trinity House, in 1836, furnishing a newly erected lighthouse,

on the Start Point, with one of these lenticular arrangements. Since that time, this apparatus, variously modified, has been gradually replacing the silvered reflectors in our British lighthouses; but only gradually-for the Board of Trade lay it down as a principle, that the expense involved by the change should only be incurred when the reflectors are worn out, and they will often last, when handled by careful keepers, for forty years. The governments of the United States and Spain have, within these last few years, instituted a complete reformation in the lighthouse service of those countries, and have adopted the lenticular system throughout.

The lenses first used in England were manufactured, we believe, at Newcastle; but they were poor affairs, and subsequently the contracts were given to French houses. But English manufacturing ingenuity was not to be baffled; and now the Messrs. Chance, of Birmingham, make apparatus equal, if not superior, to all others. A visit to their works is most interesting; and it would be instructive to describe the mysteries of the melting-pot, and the advantages of cross-stroke grinding; but space does not permit, and perhaps the reader is thankful that it does not.

Attempts have lately been made to employ pressed instead of ground glass. The chief advantage is economy; but it is an economy we do not care to practise even in our household glass, much less in optical instruments. There is a little pile lighthouse near Calais, standing in the water on its long iron legs, which is fitted up on this plan; but, though immense ingenuity has been expended on it, the experiment cannot be deemed satisfactory. It was It was at Londonderry that a lens of pressed glass first came under my notice, but the man in charge did not know which way to place the convex side; and in a tower on Lough Foyle a similar lens was actually turned the wrong way.

In the centre of this system of lenses should be the most powerful flame that can be produced. Four concentric wicks, each capable of moving independently

of the other, with a mechanical arrangement for pumping up the oil, were employed by Fresnel; and the regulation quantity of colza oil annually consumed is 785 gallons for each first-order lamp in France. Now it must be remembered, that the amount of oil burnt is pretty nearly a measure of the light produced; and, as all other expenses in a lighthouse remain the same whether the flame be great or small, it is evidently the worst economy to stint the oil. Yet this has actually been done systematically in England and Ireland, where, partly from inferiority of lamps, partly from the rejection of the fourth wick, and partly from not encouraging the keepers to burn a high flame, the quantity of oil consumed is not much more than half what it ought to be-averaging, respectively, 474 and 442 gallons in 1857. And this error tells more fatally, since it is only the light from perhaps two inches or more above the burner that ever finds its way to the sea through the lenses-so that, as the Royal Commissioners actually found in their visits, when low flames were employed, little beyond the yellow points of the flame were serviceable to the mariner.

Oil lamp with both lenses and reflec

Even in Fresnel's original design it was proposed to catch and to utilize the light which passed above the lenses by reflectors of looking glass; and several existing lighthouses contain apparatus on this principle. But the combination of the two systems has drawn forth the ingenuity and talent of the family of the Stevensons. The two systems are called, respectively, the catoptric and the dioptric, from the, common optical terms; but in this paper these terms have been hitherto avoided, and it is not my intention to trouble the reader with the distinction between catadioptric and diacatoptric, or to describe in detail an "azimuthal condensing catadioptric holophotal apparatus." It would not indeed be possible to do so without diagrams. The three following points may suffice to show the important modifications which Mr. Thomas Stevenson has made of Fresnel's idea.

The rays passing above or below the band of lenses are caught and sent into the desired direction, not by mirrors, but by totally refracting prisms of glass. The first apparatus of this character erected was at the Pedra Branca rock, near Singapore, in 1850; but the principle has been extensively adopted since. A fixed apparatus of this character is like a gigantic bee-hive, the encircling bands of which are made of glass; and, if for a first-class light, it is capacious enough for several persons to get inside it at once, and walk round the central fire, and view the image of the landscape in each separate piece of glass.

If it is desired not to illuminate the whole circle, and to send a particularly bright beam in one or two directions, as frequently happens in the narrow channels among the Western Isles of Scotland, the rays passing towards the undesired quarter are caught by lenses and a row of vertical prisms, and sent exactly to the spot where their brilliancy does good service to the sailor, winding his way through those tortuous seas.

An effective combination of the metallic reflector and the lens is in some places adopted, where the rays in front are parallized by the transparent glass, and the rest by the parabolic metal, with the exception of those at the back of the flame, which are returned through it by a spherical mirror, and sent through the lens.

It is self-evident that the proper adjustment of these different pieces of apparatus is a matter of the utmost importance; for it might easily happen that they should send the light up to the stars, or down to the shore. The Royal Commissioners suspected that in many cases it was so; and the bright idea occurred to their Secretary, Mr. J. F. Campbell, that it would be easy to determine where the light of the lamp fell on external objects, through a particular piece of glass, by observing what external object was visible through that piece to an eye placed where the flame should be. By this method of internal observation the sadly defective state of many of our lighthouses

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