Early History. The early history of Lighthouses is very uncertain; and some ingenious antiquaries, finding the want of authentic records, have been anxious to supply the deficiency by conjectures based upon casual and obscure allusions in ancient writers, and by vague hypotheses drawn from the heathen mythology. Some writers have gone so far as to imagine, that the Cyclopes were the keepers of lighthouses; whilst others have actually maintained that Cyclops was intended, by a bold prosopopœia, to represent a lighthouse itself.[24] A notion so fanciful deserves little consideration; and accords very ill with that mythology of which it is intended to be an exposition, as seems sufficiently plain from a passage in the ninth Odyssey, where Homer (who flourished about 907 B. C.), after describing the darkness of the night, informs us that the fleet of Ulysses actually struck the shore of the Cyclopean island, before it could be seen.[25]

Nor does there appear any better reason for supposing, that under the history of Tithonus, Chiron, or any other personage of antiquity, the idea of a lighthouse was conveyed; for such suppositions, however reconcileable they may appear with some parts of mythology, involve obvious inconsistencies with others. It seems, indeed, most improbable, that, in those early times, when navigation was so little practised, the advantages of beacon lights were so generally known and acknowledged as to render them the objects of mythological allegory.

It must not, however, be imagined, that ancient writings are entirely destitute of allusions to the subject of Beacon Lights for the guidance of the Mariner. The venerable poet, already noticed, in speaking of the shield of Achilles, has beautifully described the flash of a beacon-light in some solitary place, as seen by seamen leaving their friends, in those lines, which contain ample proof of the existence of such a provision for the safety of the mariner in Homer’s time:—

In the Holy Scriptures the word Beacon occurs but once, and that in Prophecies of Isaiah (xxx. 17.), who lived above 200 years later than Homer; but it is obvious that the original term, which the Septuagint translate by the word ἱστος, merely imports a flagstaff or perch and does not at all imply the knowledge of beacon-lights among the Hebrews, who were not a maritime people.

Colossus of Rhodes. About 300 years before the Christian era, Chares, the disciple of Lysippus, constructed the celebrated brazen statue, called the Colossus of Rhodes. It was of such dimensions as to allow vessels to sail into the harbour between its legs, which spanned the entrance. There is considerable probability in the idea that this figure served the purposes of a lighthouse; but there is no passage in any ancient writer, where this use of the Colossus is expressly mentioned. Many inconsistencies occur in the account of this fabric by early writers, who, in describing the distant objects which could be seen from it, appear to have forgotten the height which they assign to the figure. It was partly demolished by an earthquake, about eighty years after its completion; and so late as the year 672 of our era, the brass of which it was composed was sold by the Saracens to a Jewish merchant of Edessa, for a sum, it is said, equal to L.36,000.

Pharos of Alexandria. Little is known with certainty regarding the Pharos of Alexandria, which was regarded by the ancients as one of the seven wonders of the world. It was built in the reign of Ptolemy Philadelphus, about 300 years before the Christian era; and Strabo relates that Sostratus, a friend of the royal family, was the architect. He describes it as built in a wonderful manner in many stories of white stone, on a rock forming the promontory of the island Pharos (whence the Tower derived its name), and says that the building bore the inscription—“Sostratus of Cnidos, the son of Dexiphanes, to the Gods, the Saviours, for the benefit of seamen.” He concludes his brief notice of it by describing the neighbouring shores as low and encumbered with shoals and snares, and as calling for the establishment of a lofty and bright beacon, a sign to guide sailors arriving from the ocean into the entrance to the haven.[26]

The accounts which have come down to us of the dimensions of this remarkable edifice are exceedingly various; and the statements of the distance at which it could be seen are clearly fabulous. That of Josephus (who likens it to the second of Herod’s three Towers at Jerusalem, called Phasael, in honour of his brother) is the least removed from probability; yet even he informs us, that the fire which burnt on the top to enable seamen to anchor in sight of it, before coming near the shore, and so to avoid the difficulty of the navigation by night, was visible at a distance equal to about thirty-four English miles. Such a range for a lighthouse on the low shores of Egypt, would require a tower about 550 feet in height![27] Ammianus Marcellinus[28] and Pliny[29] are both very circumstantial in their notices of the Pharos as a beacon-light to guide seamen in approaching the coast of Egypt and port of Alexandria. The latter adds the interesting fact, that the cost of the Tower was reckoned at a sum equal to about L.390,000 of our money;[30] and both of them agree in stating that a light was shewn from it at night. Ammianus Marcellinus differs from all the other writers, in attributing the erection of the Tower to Queen Cleopatra. Pliny mentions in passing, that there were also lighthouses at Ostia and Ravenna.

If the reports of some writers are to be believed, this Tower must have far exceeded in size the great Pyramid itself; but the fact that a building of comparatively so late a date should have so completely disappeared, whilst the Pyramid remains almost unchanged, is a sufficient reason for rejecting, as erroneous, the dimensions which have been assigned by most writers to the Pharos of Alexandria. Some have pretended that large mirrors were employed to direct the rays of the beacon-light on its top, in the most advantageous direction; but, in so far as I know, there is no definite evidence in favour of this supposition. Others, with greater probability, have imagined that this celebrated beacon was known to mariners, simply by the uncertain and rude light afforded by a common fire. In speaking of the Pharos, the poet Lucian, on most occasions sufficiently fond of the marvellous, takes no notice of the gigantic mirrors which it is said to have contained. He thus speaks of this celebrated lighthouse as having indicated to Julius Cæsar his approach to the Pharos of Egypt on the seventh night after he sailed from Troy:

It is true that, by using the word “lampada,” which can only with propriety be applied to a more perfect mode of illumination than an open fire, he appears to indicate that the “flammis” of which he speaks, were not so produced. The word lampada may however, be used metaphorically; and flammis would, in this case, not improperly describe the irregular appearance of a common fire.

Perhaps, also, the opinion that some kind of lamp was used in the Pharos, may seem to receive countenance from the remarkable words of Pliny, in the passage above cited—“Periculum in continuatione ignium, ne sidus existimetur, quoniam è longinquo similis flammarum aspectus est.” The fear he expresses lest the light viewed from a distance should be mistaken for a star, could hardly be applicable to the diffuse, oscillating, lambent light derived from an open fire, and certainly gives some reason for imagining that, even at that remote time, the art of illuminating lighthouses was better understood than in the early part of the present century.

Before leaving the subject of the Pharos of Alexandria, I wish to vindicate the memory of its architect Sostratus from the calumny of Lucian, who, in his Treatise on the art of writing history, with his usual acrimony, accuses the builder of the Pharos of a fraud, in cutting his own name on the solid walls of the Tower, and covering the inscription with plaster, on which he carved the name of his royal master Ptolemy.[31] Against this assertion I would oppose the testimony of Strabo, who calls Sostratus the “friend of the Kings” (see the quotation at the foot of page 183), and the direct evidence of Pliny, who, in the passage above cited, expressly states, as a proof of Ptolemy’s magnanimity, his giving the architect liberty to inscribe his own name on the Tower. The only other notices of the Pharos which I have been able to find in ancient writers are from Cæsar’s Commentaries, Valerius Flaccus, and Pomponius Mela.[32] At Alexandria, there is a modern lighthouse called the Pharos, which is maintained by the Pacha of Egypt.

Coruña Tower Mr Moore, in his History of Ireland, vol. i., p. 16, speaks of the Tower of Coruña, which he says is mentioned in the traditionary history of that country, as a lighthouse erected for the use of the Irish in their frequent early intercourse with Spain. In confirmation of this opinion, he cites a somewhat obscure passage from Æthicus, the cosmographer. This in all probability is the tower which Humboldt mentions in his Narrative under the name of the Iron Tower, which was built as a lighthouse by Caius Saevius Lupus, an architect of the city of Aqua Flavia, the modern Chaves.[33] A Lighthouse has lately been established on this headland, for which Dioptric apparatus was supplied from the workshop of M. Letourneau of Paris.

There is also a record in Strabo of a magnificent lighthouse of stone at Lighthouse at the mouth of the Guadalquivir. Capio, or Apio, near the Harbour of Menestheus (the modern Mesa Asta, or Puerto de Sta. Maria), which he describes as built on a rock nearly surrounded by the sea, as a guide for the shallows at the mouth of the Guadalquivir, in terms almost identical with those used by him in speaking of the Pharos of Alexandria. I am not aware of any other notice of this great work, for such it seems to have been, to have deserved the praises of Strabo.[34]

Ancient Phari in Britain. In Camden’s Britannia, a passing notice is taken of the ruins called Cæsar’s Altar, at Dover, and of the Tour d’Ordre, at Boulogne, on the opposite coast; both of which are conjectured to have been ancient lighthouses. Pennant describes the remains of a Roman Pharos near Holywell, but cites no authorities for his opinion as to its use. There were likewise remains of a similar structure at Flamborough-head. A very meagre and unintelligible account is also given of a lighthouse at St Edmund’s Chapel, on the coast of Norfolk, in Gough’s additions to Camden, by which it might seem that the lighthouse was erected in 1272.[35]

Such seems to be the sum of our knowledge of the ancient history of lighthouses, which, it must be admitted, is neither accurate nor extensive. Our information regarding modern lighthouses is of course more minute in its details and more worthy of credit. The greater part of it is drawn from authentic sources; and much of what is afterwards stated is the result of my own observation, during my visits to the most important lighthouses of Europe.

The first lighthouse of modern days that merits attention, is the Tour de Corduan. Tour de Corduan, which, in point of architectural grandeur, is unquestionably the noblest edifice of the kind in the world. It is situated on an extensive reef at the mouth of the river Garonne, and serves as a guide to the shipping of Bordeaux and the Languedoc Canal, and indeed of all that part of the Bay of Biscay. It was founded in the year 1584, but was not completed till 1610, under Henri IV. It is minutely described in Belidor’s Architecture Hydraulique. The building is 197 feet in height, and consists of a pile of masonry, forming successive galleries, enriched with pilasters and friezes, and rising above each other with gradually diminished diameters. Those galleries are surmounted by a conical tower, which terminates in the lantern. Round the base is a wall of circumvallation, 134 feet in diameter, in which the light-keepers’ apartments are formed, somewhat in the style of casemates. This wall is an outwork of defence, and receives the chief shock of the waves. The tower itself contains a chapel, and various apartments; and the ascent is by a spacious staircase. The first light exhibited in the Tour de Corduan was obtained by burning billets of oak-wood, in a chauffer at the top of the tower; and the use of coal instead of wood, was the first improvement which the light received. A rude reflector, in the form of an inverted cone, was afterwards added, to prevent the loss of light which escaped upwards. About the year 1780, M. Lenoir was employed to substitute paraboloïdal reflectors and lamps; and in 1822, the light received its last improvement, by the introduction of the dioptric instruments of Augustin Fresnel, the celebrated French Academician.

Eddystone. The history of the famous Lighthouse on the Eddystone Rocks is well known to the general reader, from the narrative of Smeaton the Engineer. Those Rocks are 9¹⁄₂ miles from the Ram-Head, on the coast of Cornwall; and from the small extent of the surface of the chief Rock and its exposed situation, the construction of the Lighthouse was a work of very great difficulty. The first erection was of timber, designed by Mr Winstanley; and was commenced in 1696. The light was exhibited in November 1698. It was soon found, however, that the sea rose upon that tower to a much greater height than had been anticipated; so much so, it is said, as to “bury under the water” the lantern, which was sixty feet above the Rock; and the Engineer was therefore afterwards under the necessity of enlarging the Tower, and carrying it to the height of 120 feet. In November 1703, some considerable repairs were required, and Mr Winstanley, accompanied by his workmen, went to the Lighthouse to attend to their execution; but the storm of the 26th of that month, carried away the whole erection, when the Engineer and all his assistants unhappily perished!

The want of a light on the Eddystone, soon led to a fatal accident; for not long after the destruction of Mr Winstanley’s lighthouse, the Winchilsea man-of-war was wrecked on the Eddystone Rocks, and most of her crew were lost. Three years, however, elapsed, after this melancholy proof of the necessity for a light, before the Trinity-House of London could obtain a new Act of Parliament, to extend their powers; and it was not till the month of July 1706, that the construction of a new lighthouse was begun under the direction of Mr John Rudyerd of London. On the 28th of July 1708, the new light was first shewn, and it continued to be regularly exhibited till the year 1755, when the whole fabric was destroyed by accidental fire, after it had stood forty-seven years. But for this circumstance, it is impossible to tell how long the lighthouse might, with occasional repair, have lasted, as Mr Rudyerd seems to have executed his task with much judgment, carefully rejecting all architectural decoration, as unsuitable for such a situation, and directing his attention to the formation of a tower which should offer the least resistance to the waves. The height of the tower, which was of a conical form and constructed of timber, was 92 feet, including the lantern; and the diameter at the base, which was a little above the level of high water, was 23 feet.

The advantages of a light on the Eddystone having been so long known and acknowledged by seamen, no time was permitted to elapse before active measures were taken for its restoration; and Smeaton, to whom application was made for advice on the subject, recommended the exclusive use of stone as the material, which, both from its weight and other qualities, he considered most suitable for the situation. On the 5th of April 1756, Smeaton first landed on the Rock and made arrangements for erecting a Lighthouse of stone and preparing the foundations, by cutting the surface of the rock into regular horizontal benches, into which the stones were carefully dovetailed or notched. The first stone was laid on 12th June 1757 and the last on the 24th of August 1759. The Tower measures 68 feet in height and 26 feet in diameter at the level of the first entire course; and the diameter under the cornice is 15 feet. The first 12 feet of the Tower form a solid mass of masonry; and the stones of which it is composed are united by means of stone joggles, dovetailed joints, and oaken treenails. It is remarkable that Smeaton should have adopted an arched form for the floors of his building, instead of employing the floors as tie-walls formed of dovetailed stones. To counteract the injurious tendency of the outward thrust of those arched floors, he had recourse to the ingenious expedient of laying, in circular trenches or grooves cut in the stones which form the outside casing, tie-belts of chain, which were heated before being set in the grooves by means of an application of hot lead and became tight in cooling, after they were fixed in the wall. The light was exhibited on the 16th October 1759; but such was the state of lighthouse apparatus in Britain at that period, that a feeble light from tallow candles was all that decorated this noble structure. In 1807, when the property of this lighthouse again came into the hands of the Trinity-House, at the expiry of a long lease, Argand burners, and paraboloïdal reflectors of silvered copper, were substituted for the chandelier of candles.

Bell Rock. The dangerous reef called the Inch Cape, or Bell Rock, so long a terror to mariners, was well known to the earliest navigators of Scotland. Its dangers were so generally acknowledged, that the Abbots of Aberbrothwick, from which the Rock is distant about twelve miles, caused a float to be fixed upon the Rock with a bell attached to it, which being swung by the motion of the waves, served by its tolling to warn the mariner of his approach to the reef. From this circumstance, which formed the groundwork of Southey’s striking ballad of Sir Ralph the Rover, the Rock is said to have derived its name. Amongst the many losses which occurred on the Bell Rock in modern times, one of the most remarkable is that of the York, seventy-four, with all her crew, part of the wreck having been afterwards found on the Rock and part having come ashore on the neighbouring coast. During the survey of the Rock also, several instances were discovered of the extent of loss which this reef had occasioned; and many articles of ships’ furnishings were picked up on it, as well as various coins, a bayonet, a silver shoe-buckle, and many other small objects. Impressed with the great importance of some guide for the Bell Rock, Captain Brodie, R.N., set a small subscription on foot and erected a beacon of spars on the Rock, which, however, was soon destroyed by the sea. He afterwards constructed a second beacon, which soon shared the same fate. It was not, therefore, until 1802, when the Commissioners of Northern Lights brought a bill into Parliament for power to erect a lighthouse on it, that any efficient measures were contemplated for the protection of seamen from this Rock, which, being covered at every spring-tide to the depth of from twelve to sixteen feet, and lying right in the fairway to the Friths of Forth and Tay, had been the occasion of much loss both of property and life. In 1806, the bill passed into a law; and various ingenious plans were suggested for overcoming the difficulties which were apprehended, in erecting a lighthouse on a rock twelve miles from land, and covered to the depth of twelve feet by the tide. But the suggestion of Mr Robert Stevenson, the Engineer to the Lighthouse Board, after being submitted to the late Mr Rennie, was at length adopted; and it was determined to construct a tower of masonry, on the principle of the Eddystone. On the 17th of August 1807, Mr Stevenson accordingly landed with his workmen and commenced the work by preparing the Rock to receive the supports of a temporary pyramid of timber, on which a barrack-house for the reception of the workmen (similar to that which has already been described in a preceding part of this volume) was to be placed; and during this operation, much hazard was often incurred in transporting the men from the Rock, which was only dry for a few hours at spring-tides, to the vessel which lay moored off it. The lowest floor of this temporary erection, in which the mortar for the building was prepared, was often broken up and removed by the force of the sea. The foundation for the tower having been excavated, the first stone was laid on the 10th July 1808, at the depth of sixteen feet below the high water of spring-tides; and at the end of the second season, the building was five feet six inches above the lowest part of the foundation. The third season’s operations terminated by finishing the solid part of the structure, which is thirty feet in height; and the whole of the masonry was completed in October 1810. The light was first exhibited to the public on the night of the 1st of February 1811. The difficulties and hazards of this work were chiefly caused by the short time during which the Rock was accessible between the ebbing and flowing tides; and amongst the many eventful incidents which render the history of this work interesting, was the narrow escape which the Engineer and thirty-one persons made from being drowned, by the rising of the tide upon the Rock, before a boat came to their assistance, at a time when the attending vessel had broken adrift. This circumstance occurred before the Barrack-house was erected, and is narrated by Mr Stevenson, in his Account of the work, published at the expense of the Lighthouse Board in 1824, to which I would refer for more minute information on the subject of this work and the other lighthouses on the coast of Scotland.

The Bell Rock Tower is 100 feet in height, 42 feet in diameter at the base, and 15 at the top. The door is 30 feet from the base and the ascent is by a massive copper ladder. The apartments, including the light-room, are six in number. The light is a revolving red and white light; and is produced by the revolution of a frame containing sixteen Argand lamps, placed in the foci of paraboloïdal mirrors, arranged on a quadrangular frame, whose alternate faces have shades of red glass placed before the reflectors, so that a red and white light is shewn successively. The machinery, which causes the revolution of the frame containing the lamps, is also applied to tolling two large bells, to give warning to the mariner of his approach to the Rock in foggy weather. The erection of the Bell Rock Lighthouse cost L.61,331 : 9 : 2.

Carlingford. The most remarkable Lighthouse on the coast of Ireland is that of Carlingford, near Cranfield Point, at the entrance of Carlingford Lough. It was built according to the design of Mr George Halpin, the Inspector of the Irish Lights; and was a work of an arduous nature, being founded 12 feet below the level of high-water, on the Hawlbowling Rock, which lies about two miles off Cranfield Point. The figure of the Tower is that of a frustum of a cone, 111 feet in height, and 48 in diameter at the base. The light, which is fixed, is from oil burned in Argand lamps, placed in the foci of paraboloïdal mirrors. It was first exhibited on the night of December 20, 1830.

There are various other Lighthouses, which, in themselves, are sufficiently deserving of a separate notice, were it not that they have more or less something in common with those already described, which are unquestionably the most remarkable edifices of the kind. The first design for an Iron Lighthouses. Iron Lighthouse, is that by my Father for the Bell Rock, in the year 1800. The invention of Mr Mitchell of Belfast, for applying the principle of the screw to the erection of Lighthouses on soft foundations, deserves a longer notice than is consistent with the nature of these notes. It must therefore be sufficient to say, that the principal Lighthouses on this plan (those of the Maplin, Fleetwood, and Belfast Lough) consist of piles or of hollow pillars of cast-iron, grouped together in the form of a truncated pyramid, and closely resembling, in the general arrangement of their parts, the Beacon shewn in Plate XXX., and that erected on the Carr Rock in 1821. The lower end of each pillar is furnished with a flat screw or worm and a sharp point, which is screwed into the sand, clay, or gravel, or other soft subsoil. Mr Alexander Gordon of London also fitted up a Lighthouse, composed of cast-iron plates, which was erected at Morant, in the West Indies, a style of building in itself by no means eligible, and which seems suitable only where stone cannot be easily obtained, or conveniently applied. Both those plans (except in so far as the screw is concerned, which is indeed the distinguishing feature of Mr Mitchell’s ingenious plan) are to be found in one of my Father’s designs for the Bell Rock Lighthouse (see his Account, at Plate VII., figs. 2, 3, 4, and 5, and pp. 499, 500). Dr Potts has also invented a method of driving piles by means of atmospheric pressure, which has been used at the South Galliper Beacon, on the Goodwin Sands.

Having thus hastily described the most interesting and celebrated Lighthouses, I proceed to the proper object of these Notes, which are chiefly intended to make known the various methods now in use for the illumination of Lighthouses. There can be little doubt, that down to a very late period, Early modes of Illumination. the only mode of illumination adopted in the Lighthouses, even of the most civilized nations of Europe, was the combustion of wood or coal in chauffers, on the tops of high towers or hills. It consists with the personal knowledge of many persons now living, that the Isle of May Light, in the Frith of Forth, previous to its being assumed by the Commissioners of the Northern Lights in 1786, was of that kind; and, even in England, the art of illumination had made so little progress, that the magnificent Tower of the Eddystone, for about forty years after it came from the hands of Smeaton, could boast of no better Light than that derived from a few miserable tallow candles. Such methods were most imperfect, not only in point of efficiency and power, but also as respects the distinction of one light from another, an object which, on a difficult and rugged coast, may be considered as of almost equal importance with the distance at which the Light can be seen.

Solid substances which remain so throughout their combustion, are only luminous at their own surface, and exhibit phenomena, such as the dull red heat of iron, or of most kinds of pit-coal, and are therefore more suited for the purpose of producing heat than light. But by using substances which are formed into inflammable vapours, at a temperature below that which is required for the ignition of the substances themselves, gas is obtained and Flame. flame is produced. Much light is thus evolved at a comparatively low temperature. The gas necessarily rises above the combustible substance from which it is evolved, owing to its being formed at a temperature considerably higher than that of the surrounding air, than which it is necessarily rarer. Of this description are the flames obtained by the burning of the various oils, which are generally employed in the illumination of lighthouses. In the combustion of oil, wicks of some fibrous substance, such as cotton, are used, into which the oil ascends by capillary action, and being supplied in very thin films, is easily volatilized into vapour or gas by the heat of the burning wick. The gas of pit-coal has been occasionally used in lighthouses; it is conveyed in tubes to the burners, in the same manner as when employed for domestic purposes. There are certain advantages, more especially in dioptric lights, where there is only one large central flame, which would render the use of gas desirable. The form of the flame, which is an object of considerable importance, would thus be rendered less variable, and could be more easily regulated, and the inconvenience of the clock-work of the lamp would be wholly avoided. But it is obvious, that gas is by no means suitable for the majority of lighthouses, their distant situation and generally difficult access rendering the transport of large quantities of coal expensive and uncertain; whilst in many of them there is no means of erecting the apparatus necessary for manufacturing gas. There are other considerations which must induce us to pause before adopting gas as the fuel of lighthouses; for, however much the risk of accident may be diminished in the present day, it still forms a question, which ought not to be hastily decided, how far we should be justified in running even the most remote risk of explosion in establishments such as lighthouses, whose sudden failure might involve consequences of the most fatal description, and whose situation is often such, that their re-establishment must be a work of great expense and time. Gas is, besides, far from being suitable in catoptric lights, to which, in many cases (especially when the frame is moveable, as in revolving lights), it could not be easily applied. The oil most generally employed in the Lighthouses of England is the sperm oil of commerce, which is obtained from the South Sea whale (Physeter macrocephalus). In France, the colza oil, which is expressed from the seed of a species of wild cabbage (Brassica oleracea colza), and the olive oil are chiefly used; and a species of the former has lately been successfully introduced into the Lighthouses of Great Britain. Of all these oils, the purified sperm oil has hitherto been generally considered the most advantageous for lighthouse purposes; but there is every reason for anticipating that the late adoption of the colza oil in many of the British Lights, on the suggestion of Mr Joseph Hume, M.P., while chairman of a select committee of the House of Commons on Lighthouses, will lead to an important saving, as its combustion produces an equal quantity of light at somewhat more than one-half of the expense for spermaceti oil. Careful trials have been made of this oil; and on the 10th of March 1847, I was enabled to report the results to the Commissioners of Northern Lighthouses in the following terms:

“1. The colza oil possesses the advantage of remaining fluid at temperatures which thicken the spermaceti oil so that it requires the application of the frost lamp.

“2. It appears, from pretty careful photometrical measurements of various kinds, that the light derived from the colza oil is, in point of intensity, a little superior to that derived from the spermaceti oil, being in the ratio of 1·056 to 1.

“3. The colza oil burns both in the Fresnel lamp and the single Argand burner with a thick wick during seventeen hours without requiring any coaling of the wick or any adjustment of the damper; and the flame seems to be more steady and free from flickering than that from spermaceti oil.

“4. There seems (most probably owing to the greater steadiness of the flame) to be less breakage of glass chimneys with the colza than with the spermaceti oil.

“5. The consumption of oil, in so far as that can be ascertained during so short a period of trial, seems in the Fresnel lamp to be 121 for colza, and 114 for spermaceti; while in the common Argand, the consumption appears to be 910 for colza, and 902 for spermaceti.

“6. If we assume the means of these numbers, 515 for colza, and 508 for spermaceti, as representing the relative expenditure of these oils, and if the price of colza be 3s. 9d., while that of spermaceti is 6s. 9d. per imperial gallon, we shall have a saving in the ratio of 1 to 1·755, which, at the present rate of supply for the Northern Lights, would give a saving of about L.3266 per annum.

“Of these conclusions, the three last may be considered as more or less conjectural, being founded on data derived from too short a trial; but the striking agreement of the results obtained at the six lights in which the experiments were made, tends in some measure to supply the place of a longer period of trial; and I have no hesitation, therefore, in recommending the Board at once to introduce the use of the colza oil into all the dioptric lights, except that of Skerryvore, where some special reasons induce me to defer the change for another season. In the catoptric lights, the only reason for not making an equally extensive trial is the necessity for renewing all the burners, which require to be so constructed as to receive thick wicks of brown cotton; and it may perhaps be considered prudent to proceed with some caution in changing the apparatus, so as to suit it for burning a patent oil, the circumstances attending the regular and extensive supply of which are not yet fully known. I may remark, that I have burnt the colza oil in the solar lamp alluded to in my last report; but I disapprove of it as tending to elongate the flame vertically, and thus to decrease its horizontal volume. The elongated form of flame increases the divergence vertically where the light is lost, and so far circumscribes its horizontal range where it is most required. I have therefore substituted the thick wick burner for the solar lamp, whereby an equally complete combustion is obtained, and the proper form of the flame is at the same time preserved.”[36]