18-^7.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



385 



NEW LIGHTHOUSE APPARATUS. 



Mr. Alexander Gordon has for many years directed his talents and at- 

 tention to lighthouses, and, after extensive experience in fitting and im- 

 proving the lights, has at length produced, under the highest auspices, a 

 system of liglits so powerfully concentrated as to promise in their adoption 

 a very great advantage to ocean and river navigation. One of these lights 

 was exhibited lately at Messrs. De Ville and Co.'s manufactory, 307, 

 Strand. 



Fig. 1. 



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that a lens, or set of lenses, might be built of separate pieces of glass. In 

 1819, the late M. Fresnel proposed that the generating sections of the rings 

 not only ought not to have the same centre, but even that the different 

 centres should not be situated on the same axis of the lens. A few years 

 afterwards, M. Fresrtel engaged M. Soleil to construct eight such lenses 

 for the lighthouse of Corduan. In 182T, the Trinity Board witnessed some 

 experiments with a lens of the kind, which had been made by Mr. Gilbert, 

 under the direction of Sir David Brewster. In 1828, that b.)ard imported 

 a lens from France. In 1833, Mr. Gordon introduced a polyzonal arrange- 

 ment (both dioptric and catoptric), constructed by M. Maritz, of the 

 Hague. And, subsequently, the Trinity Board, and particularly the Com- 

 missioners of Northern Lights, at the instance of Mr. Alan Stevenson, in- 

 troduced the French system extensively in England and Scotland. In 

 1840, Mr. Gordon constructed a revolving light for Jamaica, with Hud- 

 dart's reflectors, and without refractors. In 1843, the Bermnda lighthouse 

 tower, constructed by Mr. Gordon, was lighted by Fresnel's system, con- 

 trary to Mr. Gordon's desire, who recommended very large prolate reflec- 

 tors. In 1846, he introduced a fixed light for the Point de Galle light- 

 house. 



The new system of lights exhibited by Mr. Gordon is a following out of 

 his prolate reflectors, as applied to the Ceylon lighthouse, by saving the 

 radiated light which formerly escaped past the lips of the reflector. This 

 latter portion of the light, which was formerly lost, is now bent down and 

 thrown into the beam, as shown in the annexed engraving. 



The specimen light exhibited was a single one, of great concentrated 

 power ; and although the light was only about an incli in diameter, from a 

 common Argand lamp, its dazzling brilliancy was scarcely subdued at a 

 distance of 50 yards. In this light, Mr. Gordon has combined a very pro- 

 late reflector and the refractor of Sir David Brewster deprived of its cen- 

 tral portion ; and by this system he is enabled to throw into a beam 

 nearly JJths of the whole light generated by an Argand lamp. The para- 

 bolic or conic reflector is fixed horizontally, and opens at 13i inches from 

 the light ; at a diameter of l.ii inches, and at 14 inches from the mouth of 

 the re'flector, are fixed glass zones used as the refractors, being composed 

 of four circles (earh in three pieces), varying in size and thickness,— the 

 inside face being even, and the outside of the glass cut away into curved 

 steps, to prevent useless portions from absorbing any of the light, as shown 

 in the engraving, fig. 1. 



Mr. Gordon proposes to use these new " systems" in some lighthouses 

 immediately.— For Revolving Lights : To use one or more of these sys- 

 tems, each furnished with an Argand burner, on one or more revolving 

 faces, according to the siite of the required beam.- For Fixed Lights^: To 

 use such a number of these systems as will light the circle (of 300°), or 

 any required portions of the circle ; twenty-four systems, each with its own 

 lamp, for the whole circle, and twelve systems for the half circle, and so 

 on: one system to 15°.— For Flashing or Intermitting Lights : Such com- 

 bination of these systems as the situation may require.— For Steam-ship 

 Lights, or Railway Lights : A similar but smaller system ; the source of 

 light being any that is known and convenient for the required purpose. 



Fig. 2. 

 Previously to describing the new light, we will give a short historical 

 account of lighthouse lights. About the year 1792, glass refractors, five 

 inches thick and twenty inches diameter, were substituted for reflectors, 

 the focal point being nineteen inches distant; and they were to be seen in 

 use in an English lighthouse as late as the year 1832. BulTou had pro- 

 posed to reduce such a refractor in thickness, by cutting the lens into steps, 

 so as to absorb less light. In 1811, it occurred to Sir David Brewster 



RAILWAY EXTENSION FOR SPEEDY TRAVELLING. 



If there be one thing that has more than another served the purpose of 

 retarding railway progress, it is to be found in the dogma so studiously 

 put forward on all occasions by " authorities"— meaning thereby railway 

 makers-that " Speed is Weight," even though weight be not always 

 speed. Wheiher on the broad gauge or on the narrow, weight has been 

 constantly increasing in the process of competition ; though it was evident 

 to all who took the trouble to examine, that speed was not increasing in 

 proportion to weight. Let any one examine or watch the rails on any 

 railway while an engine, with from six to nine tons on each driving-wheel, 

 is passing over them,— let any one watch the deflection of the rail, whether 

 on the continuous bearing of the broad ga^s^e or the bridge rail of the 

 narrow,-and he will be satisfied that the proce' s, even on the nominally 

 level line, is really "'at of ascending a constant gradient, varying from 

 1 in 30 to 1 in 70. The process is that of driving a wave of rail before 

 the driving wheels of the engine, just as the bows of a steam-vessel drive 

 a wave of water before them. We believe, in short, that the process of 

 propulsion on railways is analogous to skating- -that the adhesive impulses 

 are given at intervals on hard points, such as well-packed sleepers ; and it 

 is on this principle only that the constant, irregular action of the draw- 



50 



