The Electric Light Applied to Lighthouseillumination

THEELECTRIC LIGHT APPLIED TO LIGHTHOUSEILLUMINATION. 77

March 25, 1879. JOHN FREDERIC BATEMAN, F.R.SS.L.&E., President, in theChair.

MELBOURXEINTERFATIONAL EXHIBITION OF 1880. MR. BATEMAN,President, expressed the hope that the members of the Institution would assist the promoters of this Exhibition in carrying out its objects, particularly by ensuring- an adequate re- presentation of British Civil Engineering, in its widest sense, in the Southern hemisphere.

No.1,639.--“ TheElectric Light applied to Lighthouse Illumi- nation.” By JAMESR’ICHOLAS DOUGLASS,M. Inst. C.E.1 FKOMthe first establishment of lighthouses in this country, prior to A.D. 53, untillate in the last century, the luminaries were generally wood or coal fies. In 1696 tallow candles were adopted in the first Eddystone; and about 1563 rude flat-wick oil lamps were employed at the Liverpool lighthouses, in combination with reflectors surfaced withsmall facets of silveredglass, thesug- gestion of TVilliam Hutchinson, a mastermariner of that port. The invention of Argand, a citizen of Geneva, about 1780, of the cylindrical wick lamp, provided a more efficient means of illumination, which was soon generally adopted in conjunction with silvered paraboloidal reflectors ;and these again havebeen replaced by the largeconcentric-wick lamps and lenses of Augustin Fresnel. Coal-gas as a luminary for lighthouses was proposed in 1823 by SignorAldini, of Milan. It has been for many years in use in some harbour lights in this country, where gasworks are near at hand. In June, 1865, it was applied to the first order seacoast lighthouse at Howth Bailey, Dublin Bay, by the Commissioners of Irish Lights, on the system of Mr. J. R. Wigham, of Dublin, Subsequently its use has been extended to seven lighthouses on the coast of Ireland; and since July 1872 it has been under trial by the Trinity House, at the Haisbro’ lighthouses on the coast of Norfolk. The great desideratum in a lighthouse luminary would appear tobe a maximum intensity, combined with perfect focussing compactness in the optical apparatus employed, for condensing the

1 The discussion upon this Paper occupied portions of three evenings.

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 78 MINUTES OF PROCEEDINGS. radiant light into an intensified beam, and, directing it to the sea .surface for the guidance of the mariner. In these respects, neither oil nor coal-gas flames can be considered perfect. In 1837 thelate Mr. GoldsworthyGurney proposed tothe Trinity House to adopt his Bude light in their lighthouses. This light, which was produced by throwingoxygen gas into themiddle of a flame derivedfrom the combustion of ordinaryfatty oils, was, afterpreliminary experiments by Faraday, then scientific adviser to the Trinity House, practically tried at the Orford low lighthouse in 1839, when its intensity was found to be 24 timcs that of the lighthouse oil flame of the same dimensions ; but the increased cost was too great to justify itsadoption. The Drummond, or lime light, would appear fairly to fulfil the required conditions of n perfect lighthouse luminary, if it could be arranged so as to radiate freely in all directions ; but thisdoes not Beem tohave been ever accomplished. A practicaltrial of this light was made at the South Foreland high lighthouse in 1862, but the results were not SO satisfactoryas to lead the Trinity House to adopt it. Theelectric light, producd by the passage of a current of electricity betweenseparated carbon points, seems to meet most completely all the requirements of a lighthouse luminary. It is to the discovery of Faraday in 1831, and afterwards to the inge- nuity and inventive genius of Holmes, that the means are due of producing this perfect light SO as to outrival economically any other for coast illumination, where great intensityis required. The discovery of Faraday, thata magnet could produce a current of electricity in a coil of wire which approached or receded from either of its poles, is the foundation of all machines for the production of an electric current. Soon afterwards Pixii, Clarke, a,nd Saxton designed small apparatus for its application and demon- stration. Then it rested for more than twenty years without any really practical application, until Nolletconstructed a powerful magneto-electric machine for procuring,through the decomposition of water, the oxygen and hydrogen necessary for the lime light. The machine was, however, found to be a failure for the purpose intended, but this failure led to the production by Holmes, in 1853, of the firstmagneto-electric machine, powerful enough to produce electric light of sufficient intensity for lighthouse illumination. An experimentaltrial of one of Holmes’s machines was made by the Trinity House, at Blackwall, in 1857, under the direction, and to the great delight, of Faraday. A side elevation, half-endelevation, and half section of this machine are show11

on Plate 5, Fig. 1. It was mounted on a wooden framing, was about 5 feet inlength, 5 feet wide, andfeet high over all, and weighed about 2 tons. The machinecontained thirty-six compound magnets weighing 50 lbs. each, mounted in six wheels sf sixto each wheel. The helices, one hundredand twenty in number, were arranged in five rings of twenty-four to each ring. The magnets, which rotated, were driven at a speed of six hundred revolutions perminute. Direct currents were produced by the machine, through aroller commutator attached to the axle. The power absorbed by the machine was stated to be 2+ HP. After'a series of experiments, the satisfactory report of Faraday ,encouraged the Trinity House to order a practical trial of two of Holmes's magneto-electric machines in the upper lighthouse at the .South Foreland. An end elevation and a side elevation of one of the machines construct,ed for thistrial are shown on Plate 5, Fig. 3. Its dimensions over allwere: length 9 feet 3 inches, width 5 feet 6 inches, andheight 9 feet 6 inches, theweight beingabout 5i tons. The machinecontained sixty compound magnets, weighing 48 lbs. each, mounted in three vertical planes. The helices, one hundred and sixty in number, were arranged in two wheels of eighty to each wheel. In this machine the helices rotated, thus differingfrom thefirst machine; and they were driven, at a speed of ninety revolutions per minute, by a non- condensing engineacting directly on theaxle of the machine. The increased dimensions and weight of these machines were due to the stipulation that the speed should not exceed ninety revolu- tionsper minute.These machines were provided wit.ha roller commutator, through which directcurrents were produced. The power absorbed by each machine was about 22 HP. On the 8tll of December, 1858, theelectric light, produced bypermanent magnets, was shown on the sea, for the first time, from the South Forelandhigh lighthouse; and thus were magnetsserving, not only in the compass to direct the mariner in his course, but also, in producing a most intense light, to warn him of danger and guidehim on his path. The lamp used withthese and the previous experiments at Blackwall was devised by Duboscq. Duringthe early stages of the electric lightthe carbons were always maintained at the proper distance apart by hand as they were consumed. But in 1847 Staite devised a lamp, in which the upper carbonwas caused to descend towardsthe lower fixed carbon, by the current of electricity acting on an electro-magnet combined with clockwork. On this prinoiple nearly all the electric lamps since made have been constructed.

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 80 NINUTES OF PROCEEDINGS. The first complete automaticlamp for alternatingcurrents appearsto have been devised bySerrin. At this stage of the electric light manydifficulties existed in adapting it to lighthouse illumination. The trials at the South Foreland weremade with the electric luminary in the focus of the large Fresnel apparatus for fixed light, designedfor an oil flame 4 inches in diameter; consequently, the results were not so sat.isfactory as would have been obtained with an optical apparatus arranged specially for the smallerelectric luminary.The Elder Brethren of theTrinity House were, however, encouraged, under the advice of Faraday, to proceed farther with the electric light. He thus writes in his report : I beg to state that, in my opinion, Professor Holmes has practically established the fitness and sufficiency of the magneto- electriclight fur lighthouse purposes, so faras its natureand management areconcerned. The lightproduced is powerful beyond any other that I have yet seen SO applied, and in priuciple may be accumulated to anydegree ; its regularity inthe lantern is great, its management easy, andits care theremay becon- fided to attentive keepers of the ordinary degree of intellect and knowledge.”

DUNGENESSLIGHTHOUSE (Plate 3, Figs. 1). On the 1st of February, 1862, the electric light was exhibited at Dungeness, but wassuspended for nearlyfour months, the keepers being considered hardly competentto take charge. On the6th of June, 1862, thelight was permanently established. This lighthouse was erected about the year 1615, and its luminary was a coal fire until 1792, when the flames of eighteen sperm-oil lamps, in combination with 21-inch paraboloidal reflectors, were substituted; the distinctive character of the light (fixed white) being retained. The optical apparatus for the electric light was so placed in the lantern asnot to interfere with the oil-light apparatus, which was retained in case of accident. The electric luminary was exhibited in thefocus of a small dioptric apparatusof the sixthorder, having a focal distance in the central plane of 150 millim&tres, specially designed and manufactured by Messrs. Chance Brothers &; Co.,of Birmingham. Two lamps or regulators were provided, and by means of a shunting table and railway, either could be instantly brought into the focus of the optical apparatus, where, by making contact on reaching its proper position, the light was produced. A second optical apparatus immediately over the first,

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THEELECTRIC LIGHT APPLIED ,TO LIGHTHOUSEILLUMINATION. 81 was furnished with two additional lamps, so that two lamps were always in position. Whenever any defect occurred in the working .of the one in action, contact could be instantly made to light the other lamp. Thesteam engines and magneto-electric machines were erected in a room at the base of the tower, and theboilers in a corrugated iron shed near to them. Water for the boilers was obtained from a well on the premises. The ‘‘ Holmes ” lamp was of simple construction, and similar $0 those of Duboscq andSerrin, excepting that the upper and bwer carbon-holders were balanced and regulated through pulleys andsmall cat-gut bands, instead of byrack and pinions. The carbons employed inthe lamp mere a inch aquare, theupper carbon being 12 incheslong, and the lower one G inches long. The mean intensity of thelight produced at the focus of the opticalapparatus was about 670 candles. The mean intensity of the beam sent from this apparatus was, in the most illuminated plane, about 19,000 candles, being more than la.+ times the intensity of the old catoptric light, which did not exceed 1,500 candles. Before the introduction of the electric light, the establishment was in charge of one principal and one assistant lightkeeper;but for theelectric light it was necessary toadd one engineerand two assistant lightkeepers, one attendantbeing required to be constantly in the engine and boiler-room, and one in the lantern, throughouteach night between sunset and sunrise. The cost of the additional works, machinery, and apparatus for the installation of the electric light at this establishment, was nearly as follows, viz. : S. Buildingsand lantern ...... 1,866 Magneto-electric machinery and apparatus ...4,760 Total ...... 6,626

The average annual cost of the electric light during the timcit was exhibited at Dungeness (thirteen years) was nearly as follow~s, viz. : d. S. d. Wages and allowances ...... 410 6 3 Coke, coal, carbons, oil, and stores .... 442 13 2 Carriage and incidentals ...... 40 7 9 Ordinary and special repairsand renewals of) 293 buildings, apparatus, aud machinery ... Total ...... 1,186 14 11

t1878-79. n.S.1 G

To the above is to be addedinterest on the first cost and additions to the establishment, say 55,000 and $6,626 = 511,626, at 3& per cent. = 35406 18s. 2d.; thusmaking a total annual cost for the electric light establishmentof 51,593 138. Id., against 5535 9s. 8d., the totalprevious cost when the oil-flame luminary was employed. The combined intensity of the flames of theeighteen argancl burnersin the old catoptricapparatus was about 260 candles. The mean intensity of theelectric luminary was about 670 candles. The cost of each light per hour for the year of 4,412 hours (the average number exhibited per annum) would thus be 29 * 12d. per hour for the oil light, and 86 * 7d. per hour for the electric, oras 100 oilto 298 electric. If, however, the comparative cost on the quantity of light provided in the luminary at the focus of the optical apparatus beestimated, the cost per candle or unit per hour is 0.1165d. for the oil luminary,and 0-1294d. for the electric, or as 100 oil to 111 -08 electric. The. early experience with the electric light at Dungeness was far from encouraging. Frequent falling off of the light occurred from various causes connected with the machinery and apparatus, and the oil light hadoccasionally to be substituted. As no advan- tages can counterbalance thewant of certaintyin light,house illumination, no further step was taken by the Trinity House in the development of the electric light until the latter part of 1866, when favourable reportswere received from the French lighthouse authorities of the satisfactory working of the system at the two fixed lightsat Cape La HBve, the south light established in December 1863, andthe north light in September 1865. The magneto-electric machine of the Alliance Company, which soon succeeded that of Holmes, and was, from having no commutator, a marked improvement, had been adopted by the French lighthouse authoritie8, andit was found that its currentswere stronger, and the light produced more intense, than those of its predecessor. Earlyin 1867 Rolmes perfected an improvedmagneto-electric machine, without a commutator, for alternating current ; and the TrinityRouse obtained from him a pair of these machines. together with a pair of condensing ' Allen ' engines from Sir J. Whitworth & Co., each of 5 nominal HP., for a new lighthouse then about to be erected at Souter Point, nearly midway between Sunderlandand Shields. Thisapparatus, which is shown on Plate 3, Figs. 2, wassent by the Trinity House tothe Paris Exhibition of 1867, and the light was exhibited every evening on a scaffolding in the park 120 feet high, from a cylindrical lantern of 10-feet diameter, and a dioptric apparatus for fixed light

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THEELECTRIC LIGHT APPLIED TO LIGHTHOUSEILLUMINATION. 83 of the third order, or 500 millimetres focal distance in the central plane. This instrument was specially designed and manufactured by Messrs. Chance Brothers & Co., and is shownon Plate 3, Fig. 1. Anapparatus of this increased size was recommended by Mr. James T. Chance, M.A., M. Inst. C.E., as better adapted for the optical requirements connected with the electric lurninary as distinguished from anordinary flame. It has, moreover, the advantage of being nearly free from the injury found to occur to thesmaller apparatus at Dungeness, from particles of melting carbon falling on the glass surfaces. After the close of the Paris Exhibition, the lantern and optical apparatus were erected at the TrinityWharf, Blackwall, forexperimental purposes. Theim- proved magneto-electric machine of Holmes is shown on Plate 5, Fig. 2. It has nocommutator, and the alternating currents are taken off at the axle by wire brushes. These machines are driven at a speed of four hundred rovolutions per minute. Each machine absorbs 3.2 HP., and the mean light produced is 1,520 candles. Its dimensions are : length 6 feet, width 4 feet 4 inches, height 5 feet 6 inches, theweight being about 3 tons. The machine containsforty-eight compound magnets, weighing 44 Ibs. each, mounted in seven equidistant vertical planes. The helices, ninety- six innumber, are arranged in sixwheels of sixteen toeach wheel. Improved lampswere providedby Mr. Holmes with thesemachines, in which a rack and train of wheelwork were substituted for the catgut belt and pulleysfor regulating thecarbons.

SOUTERPOINT LIGHTHOUSE (Plate 4, Figs. 1). Thislighthouse waserected in 1870, andthe electric light was first exhibited in January 1871. It is situated about midway between the entrances to the rivers Tyne and Wear. The buildings comprise tower, engine and boiler house, coke store, workshop, storeroom, and dwellingsfor five men (one engineer, andfour lightkeepers). Thetower is 55 feet high, surmounted with a cylindrical helically-framed lantern 12 feetin diameter, having the focal plane of the light 150 feet above high water of ordinary spring tides. The buildings are all constructed in rubble masonry in mortar, and stuccoed in Portland cement. As nofresh water was to be found on or near the site for the boilers, an asphalted rain catch, 2,100 square yards in area, was laid around the dwellings, and four underground storage tanks, with twocooling ponds, G2

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. S4 NINUTES OF PROCEEDINGS. were constructed. The engines were provided with condensers, Are pump, and two Cornish boilers, by the Fairbairn Engineering Company, and a fog-horn apparatuswas added by Mr. Holmes. The magneto-electric machines andfog-signal apparatus were originallydriven hy frictional gearing;but this was found to wear rapidly,and caused coneiderable trouble. It has therefore been replaced by shafting, pulleys, and leather driving-belts. At Dungenessboth magneto-electric machines wererequired tobe worked to maintain a good steady light ; but atSouter Point only one machine is necessary in clear weather.When, however, the atmosphere is impaired for the transmission of light,by rain, mist, or snow, both lnachines are worked ; and with fog occurring, either by night or by day, the fog signal is sounded. Either or both of the magneto-electric machines, and the fog signal, can be worked hy eitherengine and one boiler, so thatthe complcte apparatus for the production of the electric light is in duplicate. The conducting cables between the magneto-electric machines and the lamp in the lantern are 175 feet in length, and consist of the following : Between each magneto-electric machine and B current- changer, fixed against the wall of the engine-room, there are two copper wires f inch in diameter; and from the current-changer to the lamp in the lantern there are three insulated cables, one of nineteen copper wires, No. 16 B. W. G., and two of seven wires No. 14 B. W. G. With the current from one machine, the larger and one small cable are used, the larger cable going to the upper carbon, and the smaller cable to the electro-magnet of the lamp and lower carbon. Withthe second machine added, one current is coupled with that of the othermachine, and sent through the larger cable to the upper carbon, and the other current is sent through the third cable direct to thelower carbon without passing through the elech-o-magnet. With this arrangement no alteration in the ,strength of the electro-magnet of the lamp occurs in altering the light from single to double power or from double to single power, and, consequently, no re-adjustmentof the lamp withthese changes of intensity is necessary. As an additional precaution, an oil lamp of four wicks has been fittecl to the optical apparatus, and arranged so tbat its flame can be promptly brought into focus in the case of a totd failure of the electric apparatus; but, since the first exhibition of the light on the11th of January, 1571, onlytwo important extinctions occurred for a few minutes betweensunset and sunrise. One of these extinctions was due to the keeper on watch having fallen

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THE ELECTRIC LIGHT APPLIED TO LIGHTHOUSEILLUMINATION. 85 asleep, and the other to some carbon dust having fallen on the tramwayrail of the lamp, thusinterrupting the current. The light was so speedily restored on both occasions, that it was not necessary to light the oil lamp. The distinctive character of the light is white flashing, at half-minute intervals, the light covering R sector of sea surface of 180°. The duration of each flash is five seconds, and that of each eclipse twenty-five seconds. The optical apparatus wasdesigned by Mr. James T. Chance, anit was manufactured by Messrs. Chance Brothers and Co. (Plate 4, Fig. 1). It consists of a portion of a dioptric apparatusof the third order of Fresnel for fixed light, having a focal distance of 500 milli- mBtres in the central horizontal plane. Around this apparatus i5 rotated a6 octagonal drum, each side consisting of seven vertical lenses. By theselenses the horizontally radiating beam of fixed light is gathered, and condensed into eight distinctbeams, each having 8. horizontal divergence of about 7g". These beams necessarily reach the observer at sea as the panels pass in succession before him. Owing to the small dimensions of the electric luminary, it was practicable to avoid the waxing and waning appearance of the flashes of an oil or gas light, so that they appear and disappear suddenly, are of nearly uniform intensitythroughout, and no appreciable variation occurs jn the intensity of each succeeding flash. This perfection of the flashes of the electric light doubtless. adds considerably to its distinctive efficiency. An improvement was made by the Author in the arrangement of the turntable of this apparatus. This consisted in the enlarge- ment of the roller path to thefull diameter of the apparatus, by which, besides increased steadiness and precision, access to the interior of the optical apparatus is obtained at all timcs, without the necessity of stopping it, asis usually the case, andthus altering for the time the exact character of the light. This plan has been adopted in all dioptric revolving andflashing lights since made for the Trinity House. A lower reflecting light from the same luminary as the upper light is shown from a window in the tower, 22 feet below the upperlight, for marking dangers in Sunderland Bay, distant 6 miles. The idea of thus utilising the rear lightof the luminary was suggested by the Author, and the optical apparatus for the purpose wasdesigned by Mr. James T. Chance. It consists of a glass holophote of 150 millimhtres focal distance, placed at the rear of the luminary, intercepting the landwa1-d arc of light of 135". The nearly cylindrical beam from this holophote is receive&

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 86 MINUTES OF PROCEEDINGS. on a series of straight right-angled prisms, which reflect it perpen- dicularly on to a series of nearly right-angled prisms arranged conically,and placed at the requiredlevel of the lower light. These latter prisms, which are of a form similar to those previously devised by Mr. Thomas Stevenson, M. Inst. C.E., for the Buddon- new light, reflect the beam with the proper dip to the sea surface at 4 mile from the tower to the required distance of 8 miles, and distribute it over therequired arc of 31'. There is reason to believe that this is the first instance where a lower light has been shown from the same luminary as the upperone. The system has sincebeen adopted with the first-order oil lights at the Start and Bull Point. The Author desires to express his admirat.ion of the excellent fulfilment by Mr. Chance of the optical requirements for both the upper and lower lights. Every portion of the apparatus acts in a most efficient manner. The beams have their vertical and horizontal limitsaccurately and sharply defined ; and those of theupper light, with auniform intensityat full power of about 230 times that of the electric luminary, or about 700,000 candles, are probably the most effective that have yetbeen .sent from a lighthouse. The fog signal consists of a pair of Holmes' fog trumpets, with their mouths directed seaward, and their axesseparated 90". These trumpets are fixed 87 feet seaward of the lighthouse, at an .elevation of 85 feet above high water, and are sounded by air compressed to 30 lbs. per square inch, by a pair of pumps worked by the engines. The conlpressed air is sent through an underground pipeto a receiver inthe signal house, on whichis fitted a ' Holmes ' automaticapparatus, to regulatethe intervals and duration of the blasts. The apparatus is arranged to sound every forty-five seconds, the duration of each blast being four seconds, andthe silent interval forty-one seconds. The development of sea-coast fog signals is thus aided bythe introduction of the electric light for the necessary motive power, and attendants are always ready for the production of sound during foggy weather for the warning andguidance of the mariner,when the light signal is no longer efficient. It has lately been necessary to replace the reed trumpets of Holmes by a more powerful 'Siren' trumpet, sounded by air compressed by an additional engine and boiler of 20 effective HP. It willthus be seen thatthe motive power required for a first-class fog signal is sufficient for the production of an electric light, at thefocus of the optical apparatus, with an intensity of about 25,000 candles. Theworking staff at this

lighthouse consists of one engineerand four assistant lightkeepers. Thelatter are selected men, andall have had pre- vioustraining atan electriclighthouse station;and for the specialservice they receive 10 percent. additional salary. The engineer has entire charge,of the establishment withits machinery and apparatus, and he exercises a general supervision by day, and "occasionallyduring each night, but keeps no regular watch. The watches of four hours each are kept by the four assistant keepers, me of whom is required to be constantly in the engine or boiler room, and one inthe lantern, throughout each night between sunsetand sunrise. Communication is establishedby speaking tubes between theengine room andlantern, also between the $anternand the bedroom of eachlightkeeper. The cost of the works was nearly as follows, viz. : E. Land,buildings, and lantern ...... 10,300 Magnetselcctrio machinery and dioptric apparatus . 7,000 For thc works, exclusive of fog signal . . . . . 17,300 Add cost of fogsignal . . . . , . . , . . 700 Making a total cost of . , . . . . 18,000

The average annual expenses of this establishment are nearly as follow : L. S. d. Wages andallowances ...... 397 9 2 Coke, coal, carbons, oil,and stores. . . . . 377 1 2 Carriage and incidentals ...... 20 6 7 p34 1o Odinarybuildings,and apparatus,special andrepairs machinery and renewals . . of). Total ...... 1,229 6 11

To the above is to be added interest on first cost (S17,300) at 33 per cent. = S605 OS., making a total annualcost for the electric !light establisbment of S1,534 16s. lld. The cost of the light per hour for the year of 4,412 hours is thus 99.M ; and the hourly cost per unit of light provided at the focus of the illuminating apparatus by the luminary, having a minimum intensityof 1,520 candles for 3,692 hours, and a maximum intensity of 3,040 candles for 720 hours, or a mean intensity of about 1,768 candles for the year of 4,412 hours, is 0 -0564d.,being a reductionin thecost compared with the light whenat Dungeness as0.1294 to 0.0564, or as 100 to 43.6.

SOUTHFORELAND LIGHTHOUSES (Plate 4, Figs. 2). The success with the electric light at Souter Point encourage& the Trinity House to proceed with its permanent installation at theSouth Foreland high and lowlighthouses. These two. important coast lights (each fixed white) were first exhibited in 1634, for leading vessels clear of the dreaded Goodwin Sands, throughthe Downs andup and down Channel. Thelumi- naries were coal fires until 1793, when the flames of sperm-oil lamps in conjunction with 21-inch paraboloidal reflectors were substituted. The relative positions of these two fixed lights are E. by S. and W. by K., magnetic, and their distance apart 449 yards. The focal plane of the low light is 275 feet, and that of the high light 372 feet, above high mater of ordinary spring tides. In the years 1842 and 1543 the towers were pal tly rebuilt, and new lightkeepers’ dweuiqgs were erected, from the designs of the late Mr. James Walker, Past-President Inst. C.E., and late Engi- neer-in-Chief to the Trinity House. A dioptric apparatus of the first order of Fresnel, with a four-wick concentric oil-burner \vas also substituted for the catoptric apparatus at the high lighthouse. For the erection of the requisite buildings for the electric-light machinery and apparatus, andfor the accommodation of additional keepws, the land lying between the two lighthouses was acquired: in 1869. Thebuildings comprise engineand boiler house, coke. store, workshop, storeroom, and dwellings for three men, and storage tanks for holding 35,000 gallons of water. A well, afford- ing a plentifulsupply of water for the boilers, exists on the site. This well, which is 233 feet landward from the face of the chalk cliff, is sunk 280 feet, tothe level of half-tide. It has a peculiarity conlmon .to. severalwells nearthe shores of this country, viz., that from about. half-ebb to half-flood it is quite dry, and from half-flood to half-ebb it yieldsa plentiful supply of pure spring water. This is due to the wat,er being liberated, with each tide, atan opening of thewater-bearing fissure in the chalk on the sea shore, near the half-tide level, at a distance of 450 feet from the well. The discovery by Siemens and Wheatstone, in 1867, that powerful electric currentscan be produced without the use of permanent magnets, was taken advantage of by Holmes for lighthouse illumination. In the early partof 1869 he constructed for the Trinity House, with the view to its adoption at the South Foreland, a dynamo-electric machine, which, though defective from excessive heating, was found to produce one or two lights, as required, of

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THE ELECTBIC LIGHT APPLIED TO LIGHTHOUSE ILLUMINATION. 89 great, intensity. Its powers when devoted to the production of one light were of such intensity :as hadnever been previously witnessed. Lengthened experiments were made with the machine at Blackwall by Dr. Tyndail, the successor to Faraday as scientific adviser of the Trinity House, assisted by the Author ; and photo- metric measurements of the lightproduced by themachine showed an intensityof about 2,800 candles. It was not, however, considered safe to trust themachine to the severe ordeal of lighthouse service, and the magneto-electric machines of Holmes, although of inferior power, wereadopted for theSouth Foreland. A side elevation, plan, and section of this dynamo-electric machine are shown on Plate 5, Fig. 4. The machine hasten electro-magnets, between which rotate a wheel containing t.wenty helices, at a speed of’ eight hundred revolutions per minute. The dimensions of the machine over all are: length 4 feet 4 inches, breadth 2 feet 8 inches, and height 3 feet 4 inches. Its weight is about 10 cat. The machinery and apparatus for jthe production of the electric lights at the South Forelandconsist of a pair of horizontal condensing engines, by Messrs. Hunter and English, each of 10 nominal HP. ; a pair of Cornish boilers ; four of Eolrnes’s improved magneto- electric machines, of the same model as those described for Souter Point;together with the necessary shafting, pulleys, and belts, for driving any two or all of the magneto-electric machines with either engine. Adouble-acting pumpin the deepwell is drivenby underground shafting from the engines, and a fire pump is also provided, so that in case of fire a supply of water is at hand for the service of the engine house, buildings, and dwellings, also for bothhigh and low lighthouses. The conducting cables between the magneto-electric machines and electric lamp in each lantern, together with the current-changer and the Holmes electric lamps, are of the same general form and dimensions as those describecl for SouterPoint. The conducting cables are laid underground, embedded in asphaltin 6-inch glazed stoneware pipes. The distance between the magneto-electric machines andthe lamp in the lanternof the high lighthouse is G94 feet, and between the magneto-electric machines and the lamp in the lanternof the low lighthouse 592 feet. The old lanterns were utilised for the electric. light by the removal of the vertical framing andflat glass, helical framingand cylindrical glass being substituted.The dioptric apparatus is of the same dimensions as adopted for Souter Point (third order), and was designed by Mr: James T. Chance, to meet the requirements of each lighthouse (Plate 4, Fig. 2).

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 90 MINUTES OF PROCEEDINGS. At the high lighthouse it was required to illuminate a sector of seasurface of 226', extending from the sea horizon towithin 1,174 yards of the lighthouse. At the low lighthouse it was required to illuminate 199' of sea surface, extending from the sea horizon to within 304 yards of the lighthouse. In both cases the rear or landwardarc of light, of 134O and 161" respectively, withthe exception of asmall arc required for t+e passage of thecentral pillar of the electriclamp, is utilised in aug- mentingthe intensity of the seaward light. Semi-holophotes, of 187.50 millimetres focal distance, are fitted at the rear of the luminary,and the nearly parallel beams sent fromthese holophotes are received on a panelof vertical prisms at each side of the main apparatus, and are bythese prisms uniformlydistributed over the illuminated sector. As at Souter Point, the optical requirements have been fulfilled with great precision, and the results are most satisfactory. Two electric lamps are used at each light, and these are arranged on a shunting t,able at the rear of the dioptric apparatus, in a similarmanner to that originally adopted at Dungeness. A four-concentric-wick oil lamp is fitted to each optical apparatus, as at Souter Point, to beused in case of accident to the electric light. During clearweather the current from one magneto-electric machine is sent to each lantern, as at Souter Point ; and when the atmosphere is impaired for the transmission of light, thecurrents of twomachines aresent to eachlantern. The working sta8' of this establishment consists of one engineer, and six assistant lightkeepers, previously trained at an electric light station.The watches, of fourhours each, are kept by thesix keepers. The engineerhas entire charge of the establishment, with its machinery and apparatus, as at Souter Point, and he exercises a general supervision by day and occasionally during each night. One keeper is required to be constantly in the engine orboiler room, and one in each lantern, throughout each night, between sunsetand sunrise. The distance between the engine room and thelanterns being too great forcommunication by speaking tubes, this is accomplished by Wheatstone telegraph instruments. The cost of the additional works, machinery, and apparatus for the installation of the electriclights at this establishment, which were first exhibitedin January, 1872, was nearly as follows, viz. : f. Buildings and lanterns...... 6,300 Bfegneto-electricmachinery and dioptric apparatus . 8,500 Total ...... 14,800

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THE ELECTRIC LIGETAPPLIED TO LIGHTHOUSE ILLUXINATION. 91 The average annualexpenses of this establishment are nearly as follow, viz.:

d. S. d. Wages andallowances . . . . , . . . 524 10 1 Coke,coal, carbons, oiland stores . . . . . 693 0 6 Carriageandincidentals ...... 41 8 9 Ordinaryand special repairs and renewals of 602 10 0 buildings, apparatus,and machinery . 1 . . --- Total ...... 1,861 9 3

To the above is to be added interest on the first cost and additions to the establishment, say 511.200 and 514,800 = 526,000, at 38 per cent. = ~€910,thus making a total annual cost for the ,electric light establishment of 52,771 9s. 3d., against 51,223 11s. 9d., the total annualprevious cost when the illumination was by colza oil. The combined intensity of the flame of the four-wick lamp formerly used iu the high lighthouse and the %ames of the fifteen argand oil-burners used in the low lighthouse, was about 477 5 candles. The aggregate intensity of the two electric luminaries is nearly as follows : minimum for 3,692 hours 3,040 candles, maximum for 720 hours 6,080 candles, or a meanintensity of about 3,536 candles for theyear of 4,412 hours. Theintensity of thefull- power beam sent from the optical apparatus in the high lighthouse is, in the most illuminated plane, about 152,000 candles, being about twenty times the intensity of the beam of the old dioptric oil light, which was about 7,400 candles. The intensity .of the full-power beam sent from theoptical apparatus in the low lighthouse is, in the most illuminated plane, about 131,000 candles, being about ninety times the intensity of the beam of the old catoptric oil light, which didnot exceed 1,450 candles. The cost of each description of luminary, at the focus of the optical apparatus, per hour for the year of 4,412 hours, would thus be 66 -56d. per hour for the oil luminary, and 150.7d. for the electric; or as 100 oil to 226-41 electric. Estimatingthe comparative cost on thequantity of light provided atthe focus of each optical apparatus, the cost per candle, or unit per hour, is 0 * 1394d. for the oil luminary, and 0.0426d. for the electric, or as 100 oil to 30. G electric.

LIZARDLIGHTHOUSES (Plate 3, Figs. 3). In 1573 the Trinity House determined, in consequence of wrecks occurring at the Lizard Point during fog, to provide a powerful

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 92 XINUTES OF PROCEEDINGS. fog signal, and at the same time to improve the two fixed white lights there, then catoptric oil lights. Thelighthouses were erected in 1'752, andtheir luminaries were coal fires until 1812, when .tlzese.were replaced by sperm-oil argmd lamps, in connection with 21-inch paraboloidal reflectors. A powerful Siren fog signal, combined with electric lights, was determined on as the improvement to be effectctd for the purpose of putting the coast signals of this, probably the most important landfall in Great Britain, in an eEcient state. But, before deter- mining on the apparatus to be adopted for the production of the electric light, an exhaustiveseries of comparative trials was made by the Trinit.yHouse, under theadvice of Dr. Tyndall, with various magneto-electric and dynamo-electric machines, at the SouthFore- land.The tabulated results of theseexperiments are given in Appendix A. Theinquiry led to t.he adoption of theSiemens dynamo-electricmachine and lamp. The absence of a water supply, and the experience gained by the Trinity House in the efficient and economical working of the Brown caloric engine for compressing air and sounding Sirenfog-signal apparatus,. induced the Author to recommend theseengines for the motive power; and three, each of 10 effective H.P., were ordered for the purpose, of Messrs. A. and F. Brown, of New York. An engine house, coke store, workshop, storeroom, and dwellings for four additional lightkeepers, were erected. Six dynamo-electricmachines (Plate 5: Fig. 5) were provided, each producing a mean intensity of the luminary, at the focus of' theoptical apparatus, of about 3,620 candles. These machines arearranged in three pairs, each pair being driven by a leather belt, off a pulley on the fly-wheel shaft of the caloric engines, the speed of the engine3 being sixty revolutivns. per minute, and thatof the dynamo-electric machines eight hundred and fifty. Eachpair of dynamo-electricmachines is fitt,ed and bolted to the same cast-ironbase-plate, togetherwith an inter- mediate pulley frame provided with two (driving and live)pulleys. The axle of each machine is connected to the axle of the pulley frame by a faced disc coupling and four bolts, and thus no nn- necessary strain in driving is incurred at the axle or bearings of the dynamo-electric machines. During clearweather the current. from one machine, as at the South Foreland,is sent to each lantern ; a second caloricengine, with banked fire, and its two dynamo- electric machines, being keptin readiness for immediate use. When the atmosphere is impaired, by rain, mist, or snow, for the traosmiesion of light, the second engiw is started, with its tws

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. TEE ELECTRIC LIQHT APPLIED TO LIQHTHOUBE ILLUMINATION. 93 dynamo-electric machines, andthe current from two machines coupled is’ sent to each tower, giving a mean intensity of each luminary in focus of about 8,250 candles. Whenever fog occurs the fog signal is sounded by one engine. Withthe occurrence of the fogbetween sunsetand sunrise, andwith the dynamo-electricmachines going at the time,the second caloric engine is started for the fog signal, and the fire is lighted in the retort of the third engine; but if four of the dynamo-electricmachines happento be at work at the time of the fog occurring, two are taken off the light ; the engine which was driving these is used for the fog signal, and the third engine is kept in readiness, with abanked fire, in case of accident to either of the otherengines. The caloric engines,one of which is shown in elevation, plan, and section in Plate 6, are single-acting, and consist of the following principal parts,viz., a bed-plate, heater, working cylinder,beam, Ag- wheel, air-compressing pump, and valve gear. The heater is com- posed of a cast-iron cylinder, of 37 inches external diameter by50 inches high, andis fitted witha fire-brick furnace, of 24 inches inside diameter by21 inches high, andfire-bars, Two cast-iron pipes, fitted with air-tight doors, one for access to the furnace and the other to the ash pit, areprovided. Slots are formed in these pipes, to afford communicationbetween the furnace, ashpit, and the annular space referred to. A feeding hopper is also fitted to the crown of the furnace, and is provided with two air-tightdoors, one opening outwards and the other inwards. The inner door is provided with a deflecting plate,to protect it from theintense heat of the furnace. The space between these doors is sufficient to contain fuel for one charge. The fuel (anthracite coal, or coke) is intro- duced to the furnace by closing the outer door, and depressing the inner one by means of a lever. The air pump, which is single- acting, is 25 inches in diameter, and hasa piston strokeof 20 inches. It compresses and delivers air to the heater through a channel in the bed-plate, where it supports combustion, and is expanded to a pressure of about 26 lbs. per square inch, when it is conveyed by a pipe connecting the crown of the furnace with the working cylinder, its admission being controlled by a double-beat inlet valve, actuated by a rock shaft, eccentric, and tappet-valve gear. The compressed air delivered by the air pump into the annular space of theheater enters at the bottom in the bed-plate, and passes into the furnace through the slots in the cast-ironpipes already referredto, The expended air,having done its duty in

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 94 MINUTES OF PROCEEDINGS. the cylinder, is permitted to escape into the open air by means of an outlet valve actuated similarly to the inlet valve. The down stroke of the engine is performed by the momentum of the' fly- wheel and the descending parts. The working cyhder is fitted with a trunk piston, which is kepttight by leather packing secured to the mouth of the cylinder. The engine is fitted with asensitive governor, makes sixty revolutions perminute, and works smoothly and with great regularity. The small air pump, which is alsosingle-actillg, 9 inches indiameter and 20 inches stroke, is used for compressing air to 50 lbs. per square inch for soundingthe Siren fogsignal. These engineswork upon the moderateconsumption of 30 Ibs. of coke perhour, being equal to 3 lbs. per effective HP. per hour. The conductingcables betweenthe dynamo-electric machinesanti thu lamp in each lantern, a distance of about 280 feet, consist of nineteen copper wires of No. 16 B. W. G., covered with one layer of felt tape, then insulated with pure indiarnbber, andcovered with a double layer of cotton tape, saturated with indiarubber solution, the cables having a diameter of 0.425 inch. The conductivityof the copper wire of these cables is 90 per cent. of that of pure copper. The cables are ledfrom the dynamo-electric machines along the surface of the walls at the upper partinside the buildings, and arecarried: by means of wooden suspenders secured to the wallsat every 3 feet. A current-changer is fixed to.the wall of the engine room, and is so arranged that the current from any one of the dynamo-electric machines, or any pair of machines, may be promptly sent to the lamp in either of the lanterns. The lamps, six in number, being two for each lighthouse,and two spare, are Siemens' improved form, large size, with some special additionssuggested by the Author,for meeting the requirements of 'a lighthouse..The arrangements for working these lamps in the lanterns aresame the as at the SouthForeland. The lanterns are the improved cylindrical helically framed, first older type of the Trinity House, at first intended for first order dioptric oil lights, and consequently larger than are really necessaryfor accommodatiug dioptric apparatus for the electric light. The optical apparatus for the two fixed lights, designed by Dr. Hopkinson, F.R.S., Assoc. Inst. C.E., and manufactured byMessrs.. Chance Brothers & Co., is of the same dimensions and general arrangement as thosr: atthe South Foreland; and the optical apparatus for the electric light, exhibited by the TrinityHouse at the Paris Exhibitionof 1867, and already referred to, was utilised

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THEELECTRIC LIGHT APPLIED TO LIGHTHOUSEILLUMINATION. 95 in their construction. Both lights have their focal plane 227 feet above high water of ordinary spring tides, and illuminate a sector of sea surface of 235", ext,ending from the horizon towithin 3 mile of each tower. In both the landward arc of light of 125' is utilised, inthe same manneras in the South Foreland apparatus,by holophotes andvertical prisms. In thesethe optical requirementsare fulfilled very satisfactorily.A six-concentric-wickmineral oil lampis provided, andfitted to each apparatus as a stand-by, in case of accident to the electric light. The fog signal consists of a cylindrical Siren,designed by the Author. Its form is a hollow drum, 6 inches in diameter, by 94 incheslong, having twelve longitudinal slits in its surface 8i inches long by 4 inch wide. The aperture or mouth of the trumpet corresponds in form and dimensions to one of these slits. As the drum is driven at a speed of forty revolutions per second, the compressed air, ata pressure of 50 lbs. per square inch, passing freely into the drum, is, in its passage through the slits to the trumpet, cut off twelve times ineach revolution, thus making four hundred and eighty vibrations per second. The compressed air is accumulated in two receivers, of a collective capacity of 334 cubic feet. The Siren is arranged for giTing one blast of five seconds durationevery five minutes,t,he openingand shutting of the admission valve for the blasts being effected by gearing worked from the shafting which drives the Siren. The cast-iron trumpet, 15 feet long by 18 inches in diameterat the mouth, is pivoted for sotting in any direction in azimuth over the illuminated arc, and it is always, when sounding, and with 'wind blowing at the time, pointing to the windward portion of the above arc. The working staff at this establishment consists, as at the South Foreland, of one engineer and six assistant lightkeepers. Communication is established between the engine room and lanterns, also betweeneach lanternand the bedroom of each lightkeeper,by speaking tubes, as at SouterPoint lighthouse. The cost of the additional works and apparatusfor the installation of the electric lightsat this establishment, which were first exhibited in March 1878, was nearly as follows, viz. : d. Bnildings andlanterns ...... 7,636 Dynamo-electricmachinery and dioptric apparatus . 5,500 For tho works, exolusivc of fog signal .....13,136 Add cost of fog signal ...... 1 ,SOD Making a total of ...... -14,936

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 96 MINUTES OF PROCEEDINGS. The average annual expenses of the establishment are nearly as follow, viz. : d. S. d. Wagesandallowanoes ...... 523 0 4 Coke, coal,carbons, oil, and storcs . . . . . 474 16 0 Carriage and incidentals ...... 45 0 0 Ordinary and special repaira and rcnewale of} 493 buildings, apparatus,and machinery . . . Total ...... 1,535 16 4

Tothe above is tobe added interest on the first cost and additions to the establishment, say510,564 and 513,136 = 523,700, at 3$ per cent. = 5829 lOs., thus making a total annual cost for the electric light establishmentof 52,365 6s. 4d., against Sl,Ol6 7s. Ild. when the illuminant is colza oil. The aggregate intensity of the flames of the thirty - eight argand oil- burners in the two old catoptricapparatuses was about 528 candles. Theaggregate intensity of thetwo electric luminaries is nearlyas follows; minimum for 3,692 hours 7,240 candles, maximum for 720 hours 16,500 candles, or a mean intensity of about 8,751 candles for the year of 4,412 hours. The intensity of the full-power beam sent from theoptical apparatus in each lighthouse is, inthe most illuminated plane, about 330,000 candles, being about 2llg times the intensity of the beam of each of the old catoptric lights, which was about 1,560 candles. The cost of each description of luminary perhour for theyear of 4,412 hours would thusbe 55-29d. per hour for the oil luminary, and 128.6d. for the electric, or, as 100 oil to 232.59 electric. Estimating the comparativecost on the .quantity of light provided at thefocus of each optical apparatus, the cost per candle perhour is 0.10-17d. for theoil luminary, and 0.0147d. for the electric, or as 100 oil to 14-04electric. In Appendix B is giventhe relative first cost, annual cost, intensity, and cost per unit, of the electric luminary produced at the focus of the optical apparatus at Dungeness, Souter, South Foreland,and Lizard. In Appendix C is giventhe relative consumption of coke at these stations, with the quantity of light produced in the electric lumiuary per lb. of coke consumed, and per HP. absorbed by the electric machines. It will be obeerved from these statements that the aggregate quantity of light now produced in the two Lizard luminaries is thirteen times greater than with the electric luminary when at Dungeness, and the cost per. unit of light at the Lizard is only about one-ninth of the cost perunit of the Dungenesselectric luminary. On comparing the quantity of light produced in the

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THE ELECTRICLIGHT APPLIED TO LJGHTHOUSE ILLUhfINbTION. 97 luminaries at these stations per lb. of coke consumed, the quantit,y produced at the Lizard,due to successive improvements in the electric machines and the means of driving them, is found to be twenty times greater than atDungeness.

The continuous growth seaward of the shingle point at Dun- geness,which was found in 1874, fromsurveys made by the Trinity House, to have been about 1,000 feet in eighty years, and as much as 155 feet during the preceding three years, had left the lighthouseabout 1,300 feetlandward, thus rendering necessary some better provision for marking the extreme point, The Trinity House therefore decided, until the probable future changes of the point could be more accurately determined, on placing a second low light (white, quick flashing) on a movable platform at the extremity of the point, in connectionwith a first-class Siren fog signal, the latter to replace the Daboll fog trumpet, the first instrument of this description used on the coast of this country. As the original experimental apparatus at Dungeness, both optical and mechanical, for the electric light was then tobe considered as nearly obsolete, and not more efficient than theimproved oil light, it was removed, and oil luminaries adopted for both lighthouses, the further development of the electric light being proceeded with at themore important landfall of the Lizard.

TheAuthor has been obliginglyfurnished by M. E. Allard, Director-General of the Lighthouses of France, with the following informationrelative to the adoption of the electriclight in the lighthouses of that country. The south lighthouse at Cape La HBve was lighted by electricityon the 26th of December, 1863, and the north lighthouse on the '7th of September, 1865. These are both white fixed lights. The lighthouse at Cape Grisnez was lighted by electricity on the 15th of February, 1869. This is a flashing light, showinga white flash at intervals of thirty seconds. At the Cape LaH&ve lighthouses, it' wasfound necessary to construct an engine house with coal store, workshop, rain catch, and storage tanks for water, a square room on the top of each tower for the optical apparatus, and dwellings for three additional attendants. The machinery and apparatus consist of two portable steam engines, each of 8 HP., and four Alliance magneto-electric machines,each containing forty-eight helices arranged insix wheels, and fifty-six compound permanent mapets. The lanterns which surmounted the towers when oil lights were exhibited have been removed, andthe electric lights are exhibited fromsmall [1878-79. N.s.] H

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 9s MINUTES OF PROCEEDINGS. cylindricallanterns about 2& feet in diameter,projecting from the seaward angle of the square service room, the arc illuminated by each light being275' (Plate 3, Figs. 5 and 6). The optical instruments in each tower consist of two dioptric apparatusof the sixth order, havinga focal distance in the centralplane of 150 millim8tres, placed one above the other, and similar to the arrangementadopted at Dungeness. Each optical arrangementis provided withtwo Serrin lamps ; and, in case of accident to the supplyof the electric current, an oillamp is provided, to be plaoed in the focus of the lens. The intensity of the light produced by one Alliance magneto-electric machine in a Serrin lamp is 200 becs, or French units, being equivalent to1,920 candles, or English units. During clearweather, only one magneto -electric machine is employed foreach lighthouse. Withthick weather, two magneto-electric machines are used. The intensity of the light from the optical apparatus,with the luminary of one machine in its focus, is estimated by M. Allard at 4,500 French, or about 43,200 English units. With the luminaryof two machines in focus this intensity is doubled, and would thusappear to be about 86,400 English units. The working staff at these lighthouses consists of one principal lightkeeper, fourordinary lightkeepers,and two mechanics who manage the engines and electric machines. The cost of the necessary works for the installation of the electric light at this station, and the annualcost of the two lights, is stated beto as follows :

COSTOF ADDITIONALWORKS. Francs. Buildings ...... : ..93,000 Two steam engines and accessories ...... 17,200 Four magneto-electric machines and accessories . . 50,200 Eight Serrin lamps and accessories ...... 13,000 Two lanternsand four opticalapparatus ....24,600 Erection,carriage, and sundries ...... _- 6,000 Total ...... 204,000

ANNUALCOST. Francs. Salariesto keepers, with fuel, &c...... 6,900 Coal and coke ...... 4,300 Carbons ...... 1,600 Repairs, and various other charges ...... - 3,700 Total ...... 16,500 7 At Cape Grisnez two steam engines and two Alliance magneto- electric machines are placed in a room at the base of the tower.

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THE ELECTRICLIGHT APPLIED TO LIGHTHOUSEILLUMINATION. 99 The electric light is exhibited from a small cylindrical lantern attached to the service-room, as at Cape La Hhe, theold lantern and optical apparatus being retained in case of accident to the electric light(Plate 3, Fig. 4). The optical instrument consists of a dioptric apparatus of the sixth order for fixed light, having a focal distance in the central plane of 150 millim8tres. Around this are rotated vertical lenses for producing the flashes, one lens being devoted to each flash. Thisoptical apparatus, as well as those atthe La H&ve lighthouses,was manufactured by Messrs. L. Sautter, Lemonnier & Cie., of Paris. TheAuthor is informed by M. Allard that the magneto-electric machines con- structedby the Alliance Company for Cape Grisnez are more powerful than those previouslyconstructed for Cape La H&ve, andthat the intensity of thelight produced by each machine is equal to 300 French units, or 2,880 English units. The intensity of the flash from the optical apparatus, with this luminary in focus, is estimatedby M. Allard at about 30,000 French,or 258,000 English, units. With thick weather, and both magneto- electric machines employed, this int,ensity is doubled, and would thusappear to be about 576,000 Englishunits. The working .staff employed atthis lighthouse consists of one principaland two ordinary lightkeepers, and two mechanics, who manage the

engines and electric machines. ' The cost of the necessary works for the installation of the electric light at this station, and the annual cost, is stated tobe as follows, viz. : Francs. Buildings, water tanks, &c...... 30,000 Two steam enginesand accessories ...... 12,200 Twomagneto-electric machines and accessories . . 21,300 Four Serrin lamps and accessories ...... 6,000 Lanternand optical apparatus ...... 17,500 Erection, carriage, andsundries ...... 4,000 - Total ...... 91,000

ANNUALCOST. Francs. Salaries to keepers, with fuel, &c...... 5,100 Coal,coke, &c...... 2,200 Carbons ...... 800 Repairs, and various other charges ...... 2,800 - Total ...... 10,900

A new electric lighthouse in course of erection on the Isle of Slanier, opposite Marseilles, is expected to be lighted this year; K2

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 100 MINUTES OF PROCEEDINGS. and theCommissioners of French lighthouses have recentlydecided that the Palmyre lighthouse, at %he mouth of the Gironde, shall also receive the electric light. M. Allard states as hisopinion that this light will be extended to a great number of lighthouses on the coast of France. The electric lighthouses already described, five in this country and three in France, are, with theexception of one at Odessa and one at Port Said, ail the lighthouses in which the electric light has yet been established. The Author has been obligingly informed by Captain Linden, h’aval Attache to the Russian Embassy, that at the Odessa lighthouse, where the electric light has been established about eight years, there are two Alliance magneto-electric machines and two steam engines, which are worked alternately every ten or fifteen days.Serrin regulators are used for thelight. The number of at,tendants at the lighthouse is six. According tothe report of the Director of the Black Sea Lights, the electric light at Odessa requires less attention than first order oil lights, and the extinctions of the light are less frequent. At the Port Said lighthouse, which was lighted by electricity at the openingof the Suez Canal, in November 1869, thereare two Alliancemagneto-electric machines, andtwo steamengines, each of 5 HP. The optical apparatus for thelight (white, flashing at intervals of three seconds) is dioptric of the sixth order, of 150 millimhtres focal distance in thecentral plane. A petroleum lamp is kept in readiness in case of accidents. TheAuthor has been informed that no important stoppage of thiselectric light has occurred since it was first established,

It appears to the Author desirable that, before concluding this Paper, he should attempt to show as clearly as possible the comparative cost and efficiency of lighthouseluminaries by all the agentsat present employed, viz., oil, coal gas, and electricity. Thishe is, fortunately,able to do very completely, in consequence of the Haisbro’ high lighthouse, on the coast of Norfolk, having been illuminated by gason the syst.em of Mr. J. R. Wjgham, of Dublin, for the last seven years. The cost of the additional works and apparatus for the installation of gas at this establishmentwas nearly as follows, viz. : i. Buildinga ...... 1,008 Gas apparatus ...... 988 Total ...... -1,996

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THE ELECTRIC LIGHT APPLIED TO LIGHTHOUSE ILLUBJINATION. 101 The average annual expenses of the establishment are nearly as follow, viz. :

€. S. d. Wages and allowances (three men) .... 239 0 0 Cannel and furnace coal, lime, and stores ... 141 1 10 Carriage andincidentals ...... 12 10 0 Ordinary and specialrepairs and renewals of} 136 buildings, apparatus, and machinery ... Total ...... 528 15 3

To the above is to be added interest on the first cost, and additions to the establishment, say56,674 and 531,996 = $8,670, at 34 per cent. = 5303 9s., thus making a total annual cost for the gaslight estabIishment of S832 4s. 3d. Withthe gaslight there is a minimum intensity of the luminary for clear weatherof about 832 candles,a maximum intensity for thick weather of about 2,923 candles, and a mean intensity throughout the year (4,412 hours) of 1,173 candles. In 1877 the necessary additions were made for lighting the low lighthouse (distant 766 yards) by gas, at a cost as follows, viz. : S. Additional gasometer, mains,burner, &c. ....1,296

The average annual expenses of the two lighthouses thus illuminated are nearly as follow, viz. :

d. S. d. Wagesallowances and (five men) ..... 392 2 0 Coal, oil,and stores ...... 282 3 8 Carriage andincidentals ...... 25 0 0 Ordinary and special repairs andrenewals of) 336 buildings, apparatus, and machinery ... Total ...... 1,035 5 8

To the above is tobe added interest on the firstcost and additions to the establishments, say $11,000 and 55,650 = 5316,650, at 3&per cent. = 5582 15s. ; thus making a total annual cost for the double gaslight establishment of 51,618 Os. 8d. Mr. Wigham has further developed his system by introducing the flames of two, three, and four of his large burners over each otherin the axis of the dioptricapparatus. These he calls bi- form,tri-form, and quadri-form lights. In January of last year the Commissioners of Irish Lights installed one of the quadriform lightsin a new lighthouse at GalleyHead, near Kineale. The

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 102 MINUTES OF PROCEEDINGS. intensity of the flame of a single burner used in this lighthouse during clear weather is about 1,253 candles, and the intensity of the flames of thefour burners combined, for thick weather, is about 5,012 candles. In Appendix D (see also Plate 7) is shown the comparative focussing compactness of thelighthouse luminaries which have been referredto, viz., the lights produced by oil, coal-gas, and electricity. It will be observed that, for a required maximum intensity equal to thatof the flame of the six-wick oil lamp, viz., 722 candles, the latter isa better focussing luminary than thebest of the Wigham gasflames, in theratio of 34.9 oil to 17 * 2 gas, or a5 100 to 49 3. With gas flames formed of concentric rings, similar to theflame of the large oil burner, and surrounded with a glass: chimney, the Author has found little difference, as regards com- pactnem, between them and the oil flames. The immense focussing superiority of the electric luminary as regards the best of these flames (gas or oil) is, however, found to be in the ratio of 34.9 to 21,519, or as 100 to 61,659. In Appendices E and F are shown the comparative average cost and annual maintenance of a single lighthouseshore-station in this country, withcolza oil, mineral oil, coal gas, and electricityemployed asthe illuminating agents. In Appendix E it is assumed that there is no fog signal, but in Appendix F a Siren fog signal of 20 effective HP. is considered to be provided, the motive power in the case of the gas station beingproduced by gasengines. From these statements of the cost of the luminaries per hour, andper candle perhour for theyear of 4,412 hours, it will be observed that in all cases, either with or without a Siren fog signal, where a maximum intensity of the luminary is required not exceeding that of the flame of the six-wick oil lamp, viz., 722 candles, aminimum annual cost. at the present moment is attainedwith mineral oil. For a maximumintensity exceeding this, and not exceeding about 5,000 candles, the probable limit of coal gas, the competition asregards cost liesbetween coal gasand electricity, and is infavour of the former, in consequence of the necessity for a larger number of attendants with theelectric light, five beingrequired as compared withthree for gas ; but where a maximum equal to the single or combined intensity of the Lizard luminaries is demanded, 8,250 or 16,500 candles for some of the most important coast lights, the cost of the more intenseelectric luminary is found to be perunit of light provided, irrespective of its greater value in the focus of the opticalapparatus, about and respectively of that of

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THE ELECTRIC LIGHT APPLZED TO LIGHTHOUSE ILLONINATION. 103 coal gas at its maximum intensity, and about 8 and & respectively of that of mineraloil at its maximumintensity. With intensities of the electricluminary up to about 40,000 candles, the cost per unit would prove still more in its favour, no further addition to theworking staff being necessary. It mayfurther be remarked, with reference to the electric luminary, that it isdoubtful whether any practical limit can be assigned to the intensity attainable with it, the question being limited by cost only. The development of coastfog-signals, chie%y under the direction of the United States Lighthouse Board until 1872, when the subject was made one of experimentalresearch by the Trinity House, with the co-operation of their scientific adviser, Dr. Tyndall,has resulted in instruments being provided for giving a trustworthysound-signal with minimuma range under any conditions of atmosphere of about 2 miles, and when theseconditions would obstruct even thelight of the sun at one-hundredth of the distance. It would, therefore, appear desirable that for a complete coast-light and fog-signal establishment, the highest possible intensity of light be available for coveringthe aea beyond the 2-mile rangewhenever thisis possible. The minimum intensity of the oil luminary (say 342 candles), is sufficient to cover the average geographical range of a coast light of about 17 miles in fairly clear weather; but there are many nights whenthe maximum of 722 candles is only just ableto cover the 2-milerange. Although theresults to be obtained by increased intensity,under such circumstances, are feeble when compared withthe powerexpended, so muchcan be accom- plishedby the electric light-in consequence of the enormous intensity available, combined with excessive compactness for con- densation,and direction by the opticalapparatus employed to the portion of the sea surface where it is required to reach the marinerunder varying conditions of atmosphere-that it will probably be considered of sufficient importance in many instances to justifyits additional cost. Fromthe experiments made by Faraday for the TrinityHouse, in 1836, relative to the penetrative power of lightsthrough such obstructions as fog, mist, &C., andthe expcrirnents since made bythe French lighthouse authorities and the Trinity House with oil and electric lights, it may be justly assumed that-with the atmosphere so impaired for the transmission of light that the oil luminary at its maximum intensity of 722 candles would be fairly visible at the fog-signal range of 2 miles-theelectric luminaryat its doubleLizard

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. 104 MINUTES OB PROCEEDINGS. maximum intensity of 16,500 candles would be fairly visible at about 4 miles ; farther, that on more frequent occasions, when the oil luminary would be fairly visible at about 8& miles, the electric light at theabove intensity would be visible at thefull coast-light geographical range of 17 miles.

ThePaper is illustratedby numerous diagrams, from which Plates 3 to 7 have been compiled.

[APPENDICES.

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APPENDIX C.

STATEMENTSHOWING the RELATIVECONSUMPTIOX of Corn at DUNGENESS,SOUTER, SOUTHFORELAND, and LIZARD LIGHTHOUSE^, with the QUANTITYof LIGHT PBODUCED in the ELECTRICLmmm~ PER LB. of Corn CONSUXED, and P= HF'. ABSORBED by the ELECTRICMACHINES.

%nth Fore- Dungeness Souter laud Lizarcl (One Light) heLight) rwo Lights) rwo Lights).

Tons. Tons. Tons. Annual consumption of coke in 245 95 tons ...... ) 145 153 Lbs. of coke consumed per hour lb. JbS. Iba. of light exhibited(4,412 hours)') 73-6 77.7 124.3 48.2

&density of light prodwed at focus of optical apparatus, in candles. Candle% Candlea. Minimum for 305 nights (3,692 Candles. hours) . 1,520 3,040 7,240 Maximum 'for 6d night$ (726 hours) ...... 3,040 6,080 16,500 Menn for 365 nights (4,412 1,768 3,536 8,751

Total light perannum, in candles 2,956,04( ,800,64( 5,601,28( 8,610,080 l Or as- Minimum for 305 nights . . 100 227 454 1,081 Maximum .. 60 ..... 100 454 907 2,463 Mean .. 365 ..... 100 264 528 1,306 Quantity of light (in candles) produced per lb. of coke con- 9.1 22.7 28.4 182.0 sumed ...... Or as ...... 100 249 312 2,000 Maximum quantity of light produced during 60 nights per lb. 39.1 48.9 342 3 of the total quantity of coke 9-1 consumed during 365 nights . Or as ...... 100 430 537 3, 761 Quantity of light in candles per HP. absorbed by electric ma- 222 475 475 1,097 chines ...... 100 214 214 494

1 This is inclusive of expenditure for reserve of enginepower for accidents,doubling ths iutensity of the light when requirecl, banking fires, BC.

UPENDIX D. COMPARATIVEFOCAL COHPACTKESS of LIGHTHOESE LUMINARIES.

Inches. Oil. Fresnel lamp4- i Inches. lwick . . . , . . 1 0.88 1.30 I 14 1 to 10.8 2 ,, . . . . . : 1 1.75 3.50 I 58 1 ,, 16-5 3 ,, ...... ' 2.63 1 ,, 21.4 4 ,, . . . . , . . , 3'36 1 ,, 25.6

Improved Trmity House lamps- ~

1 wick ., ...... ~ 1.00 1'63 I 23 1 ,, 14.1 2 ,, ...... 1.40 3.90 I 82 1 ,, 21.1 3 ), ...... 2.18 7'30 ' 208 1 ,, 28-5 4 ,, ...... 2.85 10.00 , 328 1 ,, 32.8 5 ,, m . . , . . . 3.73 15.43 i 514 1 ,, 33.0

6 ,, ...... ~ 4.33 20.70 ' 722 1 ,, 34.9

1 . . . .l 4.w 25-00 429 1 ,, 17'2 ... 5.88 69.38 I 832 1 ,, 12.0 . . . : ! 7.50 111.38 1,253 1 ,, 11.2 . . . . ' 9.25 148.38 2,408 1 ,, 16-1 , . . . 11.13 182.00 2,923 1 ,, 16.1 . . . . ' 12.75 213.00 3,136 1 ,, 14.7 l Electricity.

Two Lizard Intensity- ~ Minimum ...... 0.72 0.41' 8,250 1 ,( 20122.0 Maximum ...... ' 0.96 0.72 16,500 1 ,, 22916.6 Mean ...... , 0.84 0.57'12,375 l 1 ,, 21519.0

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