l:3G 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[May, 



site for ivhicli sucli an entrance as that sTiown by fiif. 16, vvas 

 adapted; the reasons for this had before been given, and were, in 

 his opinion, (piite obvious. 



Mr. Brinkl accorded fi:enerally "ith the views expressed by Mr. 

 Uendcl; lie thought, however, that althouirh tlie Institution niifiht 

 not be able to fix any rules or principles, which would evidently 

 have an injurious tendency, the mectinsrs were extremely useful, in 

 makiiif^ the profession better aequaiuted with what had been done, 

 and in affordins^ opportunities for discussing the principles of con- 

 struction and the results of certain works. 



It did not appear, that any dock entrances had been actually 

 constructed of the form and at the precise angle laid down in 

 fig. 16; now there did appear to him certain disadvantages, at- 

 tendant even upon that plan. Suppose, for instance, a rapid 

 flowing tide, with the wind setting directly up the stream and 

 across the entrance; he apprehended there would be much diffi- 

 culty in bringing the vessel to, swinging her and hauling her down 

 into the entrance. Therefore, wherever from the prevalence of 

 certain winds, such a combination of circumstances would be liable 

 to occur, no engineer would think of employing that particular 

 form; but would endeavour to find a position for the entrance 

 where an eddy existed naturally, or he would form a fore-bay to 

 produce still water, in order to facilitate the entrance of the ship. 

 It appeared also to him, that there would be considerable difficulty 

 in bringing a vessel so directly against the tide, upon leaving, as 

 was proposed. The examples that had been given were undoubtedly 

 useful; it would, however, be dangerous to assume that they af- 

 forded sufficient data whereon to base arbitrary rules for cases 

 which, to superficial observers, might appear identical; but the civil 

 engineer, whose province it was to examine, and weigh maturely, 

 all the considerations involved, would see at once that every case 

 must differ, and his skill and experience must be exercised in 

 meeting and providing for all the local difficulties. It appeared 

 therefore certain that in this, as in almost every other branch of 

 engineering, no arbitrary rules could be laid down to meet all 

 cases, and the civil engineer must be guided by his scientific and 

 practical knowledge; the great use of examples being to enable 

 him to avoid a re))etition of the errors which had been found to 

 exist and to cause inconveniences in works previously executed. 



Mr. Redman, in answer to Mr. Brunei, said there was no en- 

 trance on the Thames of the exact form laid down in fig. 16; but 

 such a fact, would not, he conceived, be urged as an objection 

 againt its ado])tion where circumstances would permit it; many 

 entrances on the Thames possessed some of its individual features, 

 — for instance, the lower wing of the Shadwell entrance of the 

 London Docks (fig. 11), and the upper wing of the Blackwall 

 entrance of the West India Dock (fig. 2) ; there were also numerous 

 examples, shown in the drawings, where vessels were docked and 

 met the tide, when leaving in the manner proposed. The conside- 

 ration of the occurrence of a rapid Hood, with the wind setting up, 

 induced him to give the preference to an angle pointing up-stream, 

 as being most available under such circumstances, and he believed 

 that to be the general opinion of persons well acquainted with the 

 system of docking vessels in the Thames. It was true, however, 

 as had been shown in the paper, that diametrically opposite 

 opinions had been entertained, which had induced constructions 

 very different to those now proposed, but which, by the addition of 

 supplemental outworks, resolved themselves very nearly into the 

 form laid down in fig. 16. The object in pointing the lower wing 

 down-streain, was to bring a vessel, when departing, head upon 

 tide. It had been already shown, that there were numerous 

 examples in the Thames, where vessels when outward-bouiul met 

 the tide at a great disadvantage, from the lower wing not affording 

 such re(piisitc facilities; a vessel leaving such an entrance as that 

 under consideration, with a warp attached to her larl)oard bow, 

 swung innnediately into the requisite position; but if the entrance 

 jiointcd up, or was even square, she would have to swing completely 

 rouml with a chance of tailing upon the ground. He could not un- 

 derstand the objection to the ])roposed forms, which he thought 

 had been misunderstood, and if a vessel could not arrive in, or 

 leave an entrance so formed, upon a river circumstanced like the 

 Thames, it was difficult to imagine the particular conformation 

 which would iirovide the requisite facilities. The fact of laying 

 down general principles for cases of engineering such as these, 

 founded u]»on the experience of the past, due consideration being 

 given at the same time to all tlie attendant circumstances, would 

 not, he conceived, lessen the duties of the engineer, as the varia- 

 tions in the level, the site, the foundation, and the construction, 

 would still demand the exercise of his judgment and e,\perience, 

 as well as his constant services, as heretofore. 



BELL ROCK LIGHTHOUSE. 

 (With an Engraving, Plate VI II. J 



Sir — I gladly embrace the op|)fntunity aff(n-ded me by your ex- 

 cellent ./«»r»a/, to correct the errors in Sir John Renuie's state- 

 ment in your number for March last (p. 77), as to the Bell Rock 

 Lighthouse, which statement, while professing to be a re])ly to a 

 letter which I addressed to liim on the 26th December last, is in 

 reality fouiuled upon a loni; correspondence between Sir John 

 Rennie and myself, which followed upon that letter. I should 

 have l>een most willing to leave the public to form their opinion of 

 the matter in discussion fr(mi that correspondence itself, which, 

 representing both sides of the question, affords, I submit, more 

 trustworthy data than the c.r parte statement of Sir John Rennie, 

 in which, I am sorry to say, by omitting some facts, and misrepre- 

 senting others, he endeavours to sup])ort his extraordinary position, 

 that the late Mr. Rennie designed and built the Bell Rock Light- 

 house. 



I have, therefore, to request that you will publish at length the 

 whole of the corresjiondence that has taken place, to which I refer 

 all who are interested in the matter. On this, as I have observed, 

 I should have been willing to rest the cimtroversy ; but certain 

 statements of Sir John Remiie, which reijuire to be exposed, com- 

 pel me to trouble you with some preliminary remarks. 



In the first place, then, I have to observe, that throughout the 

 whole of Sir John Rennie's statement, I can trace an evident 

 tendency to withhold what might seem to identify Mr. Stevenson 

 with the original design and ultimate execution of the work, and 

 to magnify, to the fullest extent, every fact that appears to support 

 his own view, — a spirit which ought not to have a place in such 

 discussions, and which has led Sir Jidin into sundry errors; but, as 

 I do not feel justified in making such a statement without proof, I 

 must trouble your readers with the following instances. 



Sir John says, that "on tlie 23rd December 1800, Mr. Stevenson 

 wrote a Report to the Commissioners of Northern Lighthmises, 

 wherein, after describing tlie locality and characteristics of the 

 Rock, he proposed tu^o designs for a Lighthouse, — one of cast-iron 

 on pillars, and another of stone." He afterwards goes on to say, 

 that the late Mr. Rennie was applied to by the Commissioners, and 

 visited the Rock in August 1805, and, "on the 30th December fol- 

 lowing, made a long Report to the Commissioners, embracing the 

 whole subject; and, after commenting at length upon the various 

 designs submitted to him, decided upon recommending a stone Light- 

 house; and observes, that as to the practicability of erecting such 

 a work on the Bell Rock, I (Mr. Rennie) think no doubt can be 

 entertained, with such examples before us as the Tout de Corduan 

 and the Eddystone." — The tendency of these statements is un- 

 doubtedly to show, that Mr. Stevenson's mind was not made up as 

 to the best structure, and that Mr. Rennie not only settled that it 

 should be of stone, but decided that it was perfectly practicable. 

 Now, Sir John states that Mr. Rennie's Report "emliraced the 

 whole subject," but he has suppressed the fact, that Mr. Steven- 

 son's embraced the whole subject also; and further, he has stated 

 that Mr. Stevenson proposed two designs, when, although be men- 

 tiinis historically that three plans had occurred to him, he jn-oposed 

 only one for adoption, viz. a stone tower, the practicability of which 

 he, at the same time, pronounced to be ckhtain. In proof of this 

 I refer to the Repm-t itself, dated 23rd December 1800, in which 

 Mr. Stevenson first details minutely the characteristics of the Rock. 

 He then describes the different works that had been executed at 

 the Eddystone, the Longship, the Smalls, the South Rock, and the 

 Tour de Corduan. all of whicli, excepting the latter, he had visited, 

 in (u-der to inform himself as to what had been done in similar 

 situations. He then proceeds to say, "that until the moment he 

 landed (ui the Rock, he was uncertain if a building of stone was 

 apjilicable;" and that, jirevious to his survey of it, and in ignorance 

 of its size, he had tliouglit./!y.yZ of a floating light, and sccuiidli/, had 

 made a design for a Lighthinise on iron pillars; but that an inspec- 

 tion of the Rock had convinced him of tlie practicability of an 

 erection of stone, which, and wliich aliine, he accordingly recom- 

 mended, as the following extracts prove. His inspection of the 

 Rock having satisfied him that the situation was more exposed to 

 be acted on by any floating body than he at first imagined, he says, 

 that "he found it difficult to suppose any set of pillars of adequate 

 strength to resist the force of a loaded vessel, which must render 

 the pillar-formed construction very uncertain." That the risk 

 attending the exposure of the metal to the action of the sea ought 

 not to be wholly o\erlooked "(» giring preference to a circular build- 

 ing of stone;" and, in conclusion, that "he has estimated the juUar- 

 formed Lighthouse at 1 j,000/., and although that for the tower of 

 masonry amounts to 42,630/. S«., yet, as it is treading a beaten path 



