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THE CIVIL ENGINEER AND ARCHITECrS JOURNAL. 



f JULY^ 



We think both of those are wrong, those who wish to make the 

 encjineer a man of book-learninf;: only, and those who want to 

 make him a boor under the name of a working-man. Brvinel, 

 Robert Stephenson, Locke, the Kennies, Walker, and many more, 

 have shown tliat to be a great engineer, and to make great works, 

 there is no harm in a man being well-taught. We would always 

 put the two together if we could, — we would have the man of 

 learning and the working-man. 



Mr. Stevenson's wav of commenting on the classics is rather a 

 new one, — rather unlike the Byzantine school, Scaliger, and the 

 Revival critics, or the great High Dutch lights of this day. Some 

 of these who went before j\Ir. Stevenson have put forth the 

 Iwild thought, that the Cyclops were the keepers of lighthouses ; 

 some Ixdder still, tliat bv the Cyclops was shadowed forth the 

 lighthouse itself. Mr. Stevenson's answer is, that in the ninth 

 book of the Odvssey, and at the U6th line. Homer tells us that in 

 tlie darkness of the night, the fleet of Ulysses went ashore on the 

 Cyclopean island. Mr. Stevenson looks at it with a workman s 

 eye, and he says if there had been a lighthouse, the ships would 

 not have struck in the dark. The words he brings forward show 

 tliat it was pitch dark, and give no hint of a lighthouse ; and 

 therefore we think Mr. Stevenson right, in the teeth of the com- 

 mentators. He has not, however, taken the trouble to set his Greek 

 into English, so that his working readers may understand it. 



^\'llat Mr. Stevenson says of the lighthouses of our days is the 

 more worthy of being read, as he has seen many of them himself, 

 and looked at them with the eye of a master. 



Speaking upon lighting, Mr. Stevenson says, that down to a very 

 late time, the only way was to burn wood or coal in chafing dishes 

 on the tops of high towers or hills. Many now living know that 

 the Isle of May light was of that* kind, before it came under the 

 care of the Board of Northern Lights in 1786. For forty years 

 after the time of Smeaton, the fine tower of the Eddystone was 

 lighted only with tallow candles. These lights were therefore 

 very weak, and there were no means of knowing one light from 

 another, so that the seaman might shape his way. Even now, it 

 too often happens that seamen mistake lights, and by going 

 inside, instead of outside or otherwise, they go aground and are 

 wrecked. The old lighthouses were of little more good than to 

 give warning that land was near ; so that ships might, if they 

 could, lie by or put out to sea until daylight, 

 lilr Stevenson now speaks of flame. He says: — 

 " Solid substances which remain so throughout their combustion, are only 

 luminous at their own surface, and exhibit phenomena, such as the dull red 

 beat of iron, or of most kinds of pit-coal, and are therefore more suited for 

 the purpose of producing heat than light. But by using substances which 

 are formed into inflammable vapours, at a temperature below that which is 

 required for the ignition of the substances themselves, gas is obtained and 

 Jlaine is produced. Much ligiit is thus evolved at a comparatively low tem- 

 ncralure. The gas necessarily rises above the combustible substance from 

 wiiicli It is evolved, owing to its being formed at a temperature considerably 

 liigher than that of the surrounding air, than which it is necessarily rarer. 

 Of this description arc the flames obtained by the burning of the various oils, 

 which are generally employed in the illumination of lighthouses. In the 

 combustion of oil, wicks of some fibrous substance, such as cotton, are used, 

 into which the oil ascends by capillary action, and being supplied in very 

 tliiu films, is easily volatilized into vapour or gas by the heat of the burning 

 wick. The gas of pit.coal has been occasionally used in lighthouses ; it is 

 conveyed in tubes to the burners, in the same manner as when employed for 

 domestic purposes. There are certain advantages, more especially in dioptric 

 lights, where there is only one large central flame, which would render the 

 use of gas desirable. The form of the flame, which is an object of consider, 

 able importance, would thus be rendered less variable, and could be more 

 easily regulated, and the inconvenience of the clock-work of the lamp would 

 be whollv avoided. But it is obvious, that gas it by no means suitable tor 

 the majority of lighthouses, their distant situation and generally difficult 

 access rendering the transport of large quantities of coal expensive and uncer- 

 tain ; whilst in many of them there is no means of erecting the apparatus ne- 

 cessary for manufacturing gas. There are other considerations which must 

 induce us to pause before adopting gas as the fuel of lighthouses ; for, 

 however much the risk of accident may be diminished in the present day, it 

 still forms a question, which ought not to be hastily decided, how far we 

 should be justified in running even the most remote risk of explosion in 

 establishments such as lighthouses, whose sudden failure might involve con- 

 sequences of the most fatal description, and whose situation is often such, 

 that their re-establishment must be a work of great expense and time. Gas 

 is, besides, far from being suitable in catoptric lights, to which, in many 

 cases (especially when the frame is moveable, as in revolving lights), it could 

 not be easily applied. The oil most generally employed in the lighthouses 

 of England is the sperm oil of commerce, which is obtained from the South 

 Sea whale {P/it/seter macrocephalvj). In France, the colza oil, which is 

 expressed from the seed of a species of wild cabbage (Brasjtca oleracea colza), 



and the olive oil are chiefly nsed ; and a species of the former has lately been 

 successfully introduced into the lighthouses of Great Britain." 



Sperm oil is that which has been hitherto most burned ; but 

 colza oil will, it is thought, be found much better, and that a 

 saving of one-half can be made. It was Mr. Joseph Hume, when 

 chairman of a committee of the House of Commons on Light- 

 houses, who showed that colza oil was cheaper. Since then, Mr. 

 Stevenson has tried it, and has told the Northern Lighthouse 

 Board that it will give a saving of £3,266 yearly ; but since that, 

 colza oil is worth more, and Mr. Stevenson is not so strong in his 

 feeling about it. 



Of the Drummond and Voltaic lights, the writer says : — 



" The application of the Drummond and Voltaic lights to lighthouse pur. 

 poses is, owing to their prodigious intensity, a very desirable consummation ; 

 but it is surrounded hy so many practical difScuIties that, in the present 

 state of our knowledge, it may safely be pronounced unattainable. The 

 uncertainty which attends the exhibition of both these lights, is of itself a 

 sufficient reason for coming to tliis conclusion. But other reasons unhappily 

 are not wanting. The smallness of the flame renders them wholly inappli- 

 cable to dioptric instruments which require a great body of flame in order to 

 produce a degree of divergence sufficient to render the duration of the flash 

 in revolving lights long enough to answer the purpose of the mariner. M. 

 Fresnel made some experiments on the application of the Drummond light to 

 dioptric instruments, which completely demonstrate their unfitness for this 

 combination. He found that the light obtained by placing it in the focus of 

 a great annular lens was much more intense than that produced by the great 

 lamp and lens; but the divergence did not exceed 30'; so that, in a revolu- 

 tion like that of the Corduan light, the flashes would last only 1^ second, 

 and would not, therefore, be seen in such a manner as to suit the practical 

 purposes of a revolving light. The great cylindric refractor used in fixed 

 lights of the first order, was also tried with the Drummond light in its focus; 

 but it gave coloured spectra at the top and bottom, and only a small bar of 

 white light was transmitted from the centre of the instrument. The same 

 deficiency of divergence completely unfits the combination of the Drummond 

 Ught with the reflector for the purposes of a fixed light, and even if this 

 cause did not operate against its application in revolving lights on the 

 catoptric plan, the supply of the gases, which is attended with almost insur- 

 mountable difficulties, would, in any case, render the maintenance of the 

 light precarious and uncertain in the last degree. 



The Drummond light is produced by the ignition or combustion of a ball 

 of lime (|- inch diameter) in the united flames of hydrogen and oxygen gases, 

 and is equal to about '261 flames of an ordinary Argand lamp witb the best 

 spermaceti oil. It deiives its name from the late Lieut. Drummond, R. E., 

 who first applied it in the focus of a paraboloid for geodetical purposes, and 

 afterwards proposed it for hghthouses. (See his account of the light in 

 the Phil. Trans, for 1826, p. 324, and for 1830, p. 383.) The Voltaic light 

 is obtained by passing a stream of Voltaic electricity from a powerful battery 

 between two charcoal points, the distance between which requires great 

 nicety of adjustment, and is the chief circumstance which influence the 

 stability and the permanency of the light. The Voltaic light greatly exceeds 

 the Drummond light in intensity, as ascertained by actual comparison of 

 their effects ; but the ratio of their power has not been accurately determined. 

 It was first exhibited in the focus of a reflector by Mr. James Gardner, 

 formerly engaged in the Ordnance Survey of Great Britain." 



After speaking of what Argand did, and of the burner he mad«, 

 which was such a great step, Mr. Stevenson comes to the reflector : 



" The name of the inventor of parabolo'idal mirrors and the date of their 

 first application to lighthouses, have not been accurately ascertained. The 

 earliest notice which I have been able to find, is that by Mr. William 

 Hutchinson, the pious and intelligent author of a quarto volume on ' Practi- 

 cal Seamanship' (published at Liverpool in 1791), who notices (at p. 93) 

 the erection of the four lights at Bidstone and lloylake, in the year 1763, 

 and describes large parabolic moulds, fashioned of wood and lined with 

 mirror-glass, and smaller ones of polished tin-plate, as in use in those light- 

 houses. Mr. Hutchinson seems to have understood the nature, properties, 

 and defects of the instruments which he describes, and has shown a good 

 acquaintance with many of the most important circumstances to be attended 

 to in the illumination of lighthouses. Many claims to inventions rest on 

 more slender grounds than might be found in Mr. Hutchinson's book for 

 concluding him to have first invented the paraboloidal mirror and applied It 

 to use in a lighthouse ; but, in the absence of any statement as to the date 

 when the mirrors were really adopted, the merit of the improvement must, 

 in justice, be awarded to others. 



M. Teulere, a member of the Royal Corps of Engineers of Bridges and 

 Roads in France, is, by some, considered the first who hinted at the advan- 

 tages of paraboloidal reflectors ; and he is said, in a memoir dated the 26th 

 June 1783, to have proposed their combination with Argand lamps, ranged 

 on a revolving frame, for the Corduan lighthouse. Whatever foundation 

 there may be for the claim of M. Teulere, certain it is that this plan was 

 actually carried into effect at Corduan, under the directions of the Chevalier 

 Bnrda ; and to him is generally awarded the merit of having conceived the 

 idea of applying paraboloidal mirrors to lighthouses. These were most 

 important steps in the improvement of lighthouses, as not only the power of 



