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.--“ The Electric 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 master mariner of that port. The invention of Argand, a citizen of Geneva, about 1780, of the cylindrical wick lamp, provided a more efficient means of illu- mination, 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 Signor Aldini, 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 to have 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 between separated 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 pro- duction 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 illumi- nation. 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 Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [16/09/16]. Copyright © ICE Publishing, all rights reserved. THE ELECTRICLIUHT APPLIED TO LIGHTHOUSEILLUMTNATION. 79 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 six to 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 hun- dred revolutions per minute. Direct currents were produced by the machine, through a roller 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 Foreland high 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 ex- hibited 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.