MODERN LIGHTHOUSES

New Zealand Mail, Issue 1679, 4 May 1904, Page 77 (Supplement)

MODERN LIGHTHOUSES

“It is some consolation to find that -there is one ‘biggest thing" in the wo riel •which Americans do not yet possess, and that is the biggest flashlight/" This sentence, which appeared recently in The London "Tit-Bits/" introducing a description of the new' electric flashlight ree©u\ly erected by the German Government on the. island of Heligoland, led one of those citizens of the United States jealous for the supremacy of his native land to write a letter challenging the veracity of this statement.' Hig country, ne asserted, was the home of the mpest powerful flashlight. He referred to the light of IN!avesiiik Highlands, which replaced! the old. twin lights five years ago, and, according to the writer of the letter, throws a beam light having a candle power of 80,000,000, as compared with, a candle power of 30,000,000 at Heligoland. 'So far as can be learned, the challenger is right to the extent that the Highlands Light is more powerful, but it is doubtful if .it is as powerful as he declares it to’ be. The manufacturers of the light declared its capacity to be 90,000,000 candle power, but officials of the lighthouse establishment who have measured it cut those figures in two, giving it credit for 45,000.000 The Highlands Light is the one most sought for by the navigating officers of incoming steamships after sighting the flashing eye of Hie Fire Island Light, the first seen on the" Atlantic Coast. This beam of light, swung around the horizon every five seconds', and seen only for a tenth of a second, is the light for which the navigator is seating. It is directly visible from the bridge of a steamship at a distance ol thirty miles if the atmosphere be clear, and it is asserted that its reflection on the clouds has been seen at a distance of ICO miles. Few persons outside of those connected with lighthouse establishments realise the marked' improvements which have been made in lighthouses, widening their sphere of -usefulness. Prior to the year 1822 the optical apparatus used in the best. equipped lighthouseg was a silverplated parabolic reflector., Th© power of a first Older reflector light of sixteen re..fieciiGTs, ranged on a frame having four faces was equal to 9340 candles. In place of the reflectors to-day lenses are used, which multiply the light of an oil lamp to many times that of the early reflec-tors,-and which converge the rays above and below the centre of the light unit l !

they are parallel to those thrown out from the centre, the whole going forth in one straight shaft. So difficult is it to make these lenses and prisms that there ar© only four places in the world where they are made—one in England and three in France, the home of lenses-. One of these sets- of lenses was given to one of the most prominent American optical firms to copy, but after nearly a year of experiment the attempt was abandoned. Therefore Uncle Sami is compelled to buy most, of his equipments in Europe. The cost of the Lenses run as high as A 6300. Even when repairs are to be made it is necessary to return the lenses to the makers. One would think that they beior of heavy glass, would seldom require repairs, but th© visitors to so-m-ei of the- tall lighthouses on the Long Island 1 coast have doubtless observed, how badly nicked are the keen edges of the prisms. The keeper of one of these lighthouses wag asked for the cause of the damage. ‘'Th© birds did it/" lie replied. “When the geese and ducks are migrating they dash themselves against the plate glass outside, and when the glass breaks the pieces fly against the lenses and - break them./" This plate glass is of considerable thickness, but the birds strike it with a force that not only breaks the glass panels, but kills the birds themselves. Th© keeper said on these occasions he invariably had a gams dinner the following day. The great difficulty in constructing the lenses lies in combining the prisms' in such a way that every ray shall lie parallel with every other ray from their source to the pilothouse of a vessel just appearing over the horizon, from ten to twentyfive miles array. The variation of a slight fraction of an inch at the lens would be exaggerated many thousandfold at the horizon. Tine lens- of the Highlands Light is of the bivalve type, so called because it consists of two convex sets of lenses' and prisms, joined together at the edges by heavy brass bands-, which concentrate all the iight into two beams. By means of this concentration, a mor© intense light is obtained tram. a guven size of lamp than is ■ possible from th© older style o. lens distributing the light throughout tli© entire 3SOd-eg. 'The flash is usually obtain-' ed by moving the -entire lens around the light on ball -bearings. The apparatus at the Nave-ink Highlands weighs forty-five tons, ana could not be moved on ball bearing's readily; therefor© ft is floated on mercury, and can be moved with a touch of the finger. The method of utilising more than one tower to give light stations identifying characteristics is an expensive one, as it involves the operation of more than one light, besides- keeping the house in repair. By th© improvement of lenses and. the clockwork by which revolving lights are operated!, it -has been made possible greatly to vary the characteristics of the light. As a foundation there are the two colours, white and red, and the revolving apparatus. The variations are fixed white combined with' a white flash, a fixed red with a red flash, a fixed white with red flashes of different numbers, flashes with intervals of different lengths, combination of white and red) flashes, lights Which show white in certain directions and red in other directions. Several of these combinations can be seen in New York Harbour and the neighbourhood. The well-known light at th© westerly end of Lorig Island 'Sound on Execution Rock is a light which flashes white, except in one sector in which the flashes are red. The Hell Gate port light has flashes of three seconds’ duration, alternately whiteand red. The North Hook Beacon on gaudy Hook has a fixed whit© light,, with, a fixed red- sector covering the water, beneath which li© th© cables operating the electric buoy© in th© Gedney and Baysidie channels. Vessels are forbidden to

anchor in the red light district. The centre of the main ship channel leading into Salem Harbour is marked on th© water by a stronger light than that on either side. The light is a fixed white, a lens panel greatly increasing its intensity being placed on the side of the lantern opposite the channel. At Montank Point the main light is a revolving light. A fixev* red light placed in a lic-tlo balcony just beneath th© main lantern sheds a warning light over a reef of the north side ol the point. Th© lime of keys which fringes- the Florida cons' from tine Poway 1 cocks to Dry Tor lug as is marked by a continuous band oi -ed light furnished -by a. series of lighthouses provided with red sectors, whose rays inter sect. A vessel attempting t-o cross the danger line would be man© aware of the fact at whatever point the aiueimpt was made. The remaining sectors of the lights in some oases are wiute, fixed, or flashing. The Gape Charles light signals “45’" every minute. : There are four flashes, io hewed by an eclipse of six seconds, and then five flashes, 10l lowed by an eclipse of thirty-two secon da. The colour ol a fixed or revolving light which dc-:-s not change is given by the colour of ills chimney on th© lamp within the lens. In cases where a red light is to be thrown in a given direction a piece of red glass is* placed in such a position that all tine light thrown m that direction, whether Irani a fixed or revolving light, will pass through it. Whenever there is to be a combination of white and red flashes, certain of the panels, the number being determined by the number of red flashes and their frequency, ace covered with red glass, which moves with the revolving lens. The interval bereween th© flashes is determined by th© speed wall which the lens i-si carried around. T'iie flashes are not uepeurated by dark panels' as one might imagine. The separation is due to th© form of the lenses, which concentrate the rays passing through a given, panel and protect ifiieuu in a single beam instead; ,of scattering tnem througiiout the. entire &4*e>, wii*cn would be covered by a fixed light from that panel. These beams, therefore, are more brilliant than those from a fixed light.—“ New fork Tribune/"