382 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



QDecembeb, 



Mr. Buchanan Ihen procepdeil to give an interesting description of the 

 situation of the bridge, the romantic shores of the estuary, the extraordi- 

 nary phenomena of its tides rushing in from the great sea at either extre- 

 mity, and producing, by tiie concurrence of waters and other circum- 

 stances, peculiar anomalies, and, al)ove all, currents, running often at the 

 rate of seven and eight mdes an hour ; and lastly, the extraordinary and 

 exciting operations connected with the launching of the first great tube, 

 Hnd floating it through those waters and currents; the difficulties, the 

 dangers, and the singular incidents which occurred during the brief and 

 trying moments of this extraordinary enterprise, but which, by the long- 

 matured aud perfect arrangements previously made, ail ended in depositing 

 it .-afely on its site between the piers. 



The next great operation to be described was that of the lifting of the 

 lube, but the description of which, owing to the important business before 

 liie Society this evening, of distributing the annual prizes to the successful 

 competitors for Inventions anil C'oinmnuications, was necessarily deferred 

 to another evening. In lonclusicjn, particular reference was made to the 

 great work which is now preparing by Mr. Edwin Clarke, with Mr. Ste- 

 p.ienson's sanction aud advice, being a history and description of the Con. 

 way and Britannia Tubular Bridges, with all the operations, and Illus- 

 trated by very Dumerous drawin-s, on a large scale, of the details of the 

 work, and also an account of I he various experiments on the strength of 

 iron, rivetted joints, &c., some of the results of which, as communicated 

 to him by JMr. Clarke, he would state at the next meeting. 



INSTITUTION OF CIVIL ENGINEERS. 



Nov. 13 ami 20. — Joshua Field, Esq., President, in the Chair. 

 In accordance with the resolution of a special meeting of Members, the 

 Session of the Institution commenced nn the 13th ult., instead of, as hereto- 

 fore, in the middle of January. This is a great improvement, as it assimi- 

 lates the routine of this useful Society to that of other scientific bodies; it 

 will also prove very convenient to the country members, give a greater iiura- 

 ber of meetings, and enable the Session to terminate lirilliantly witli the 

 President's conversazione. The annual general meeting for the election of 

 President, Council, and OtBcers, is appointed to take place on Tuesday, De- 

 cember 18th. 



The paper read was a "Description of the Cufferdam at the Grimsby 

 Dovki. By Mr. Charlfs Neate. A.Inst. C.E. 



The author commenced by briefly noticing the importance of preliminary 

 structures iu all works of hydraulic engineering, and the difficulties gene- 

 rally attending their exi-cution. The position of Grimsiiy, on tiie south shore 

 of the Hnmber, was then described ; its proximity to the sea; the natural 

 shelter afTorriiil liy the opposite shore of Spurn llead ; and the various ad- 

 vantages it presented for the construction of extensive docks. A general 

 description followed of the enclosure made for the purpose of tlie dock- 

 works, which comprised an ,irea of 138 acres, and projected five-eighths of 

 a mile beyond the margin of the high-water line of the shore. It was ex- 

 plained that the flatness of the coast necessitated tliis great |>rojectinn, as it 

 «as requisite to found the new cnirance locks in llie low-wati-r channel of 

 tlie river, in order to secure, at all times, a suffiiient deptli of water for large 

 vessels. These conditions regulated the position of the coftVrdam, which 

 stood in a very exposed siumlion, and was entirely self-supported; its prin- 

 cipal features were stated to be its extent, anri the form ol its construction. 



I he hngth of the cofferdam w.is l.iOO feet, su|iporling at high water a 

 head of water of 2S feet, whiKt the excavation behind it was carried to 



I I feet below low water. The form of the dam was that of a circular curve, 

 v^ith a versed sine of 200 feet, or nearly one-fiflh of the span. 



Several of the constructive arrangenients were peculiar; the work con. 

 sisted ol a triple row of whole timber sheet-piling, which derived interior 

 support from counterforts or buttres?es of solid sheet-piling, driven at inter- 

 vals of 25 feet throughout its length. The long or through-bolts were tuade 

 to break jnint and terndnale at the mirldle row of piling, so that no water 

 ccuhl pass along them thrnuch the dam. In the middle row of piling, 

 wroupht-iron plating was substiluled for timber wabngs, which formed ex- 

 cellent longitudinal ties, and left an iminterrupted surface nn the piling, 

 apainst which the puddle would lie compactly. It was stated that these 

 arrangements had imparted an extraordinary degree of stability and tight- 

 ness to the strni'ture, which had resisted the etfeets of storms, and the pres- 

 sure of the tides, in the most perfect manner, during a period of fourteen 

 iiionths. A ponion of the ground between the works and the shore was 

 riescrihed as being of a soft silty clay, probably the site of an old channel; 

 iuid as it was found, after all precautiiiiis, impossilile to raise any solid struc- 

 ture U|ion it, the alternative was adopted of displacing it completely, by 

 r. ising a batik of chalk-stone rublile, which sunk down to the hard bed of 

 cl.iy beneath. This method was successful in forming a very fine embank- 



IIK-llt. 



The abundant supply of water from Artesian wells in Giimshy was ad- 

 verted to, and referred to the vicinity nf the chalk hills. 



The coiiclnsinn of the paper drew attention to the magnitude of the ma- 

 sonry woiks now ailvanciii;; at Giiinsby, and for the formation of which the 

 C' Ifiidain was erected, ai:d wliicb, when conipkted, from the designs of Mr. 

 Utiidel, the chief engineer, and under the superintendence of Mr. Adaiu 



Smith, the resident engineer, will form perhaps one of the most useful, as 

 well as the most important, maritime works of modern times. 



The Dean of Westminster made some remarks on the advantages that 

 would result, from engineers possessing a more accurate knowledge of geo- 

 logy, and being able to discriminate between strata by an examination of tha 

 component parts, and to decide upon their origin, as a guide in judging of 

 their capability of supporting the weights likely to be placed upon them ia 

 the construction of works, lie gave many instances where, in his opinion, 

 more accurate geological knowledge would have secured greater success, or 

 have prevented casualties. He quoted particularly the borings and the report 

 said to have been made previous to the commencement of the Thames Tun- 

 nel, and the recent statement, that the projected tunnel for receiving and 

 conveying the sewage of London down to the Essex marshes, would, through- 

 out its entire length, have been in the London clay. He showed, however, 

 that no London clay was to be found eastward of St. Paul's, and that the 

 plastic clay was constantly mistaken for it, in consequence of the observers 

 not possessing a sufficiently accurate knowledge of the difl'erence in the con- 

 stituent features ot the two clays. 



Mr. Rendel and Mr. Brpnel, although they admitted that an accurate 

 knowledge of geology was most valuable to the profession, contended that 

 engineers were not so ill-informed on the subject as had been assumed; they 

 iliii appreciate the necessity of that knowledge, and although they might not 

 he able to discnurse upon it with the eloquence of a Buckland, a Lyell, or a 

 Sedgwick, or to speculate so plausibly upon the events of past ages, no 

 careful engineer ever decided upon the position, or mode of construction of 

 his works, without a series of trial borings, a careful examination of the 

 specimens, and experiments on them, cbii fly with the view of ascertaining 

 their strength, or cafiability for sustaining weights. Instead, therefore, of 

 accusing engineers, of knowing so little, it was rather a sutiject of surprise 

 that they knew so much ; for no profession demanded such varied acquire- 

 ments, or the exercise of such general common-sense and judgment. It was 

 shown, that the position of the Thames Tunnel was not determined by the 

 report, or the results of the borings, but with a view to establishing a con- 

 nection between particular localities. The borings were perhaps inefficiently 

 made, as compared with those of the present day, with the improved appa- 

 ratus now in use; but Mr. I. K. Brunei had made a very complete series of 

 borings across the Thames, showing most accurately the strata of the bed, 

 and no errors could have been induced by them. — The statement of the pro- 

 posed sewer tunnfl being in the London clay, never had been accepted by 

 eminent men, who understood their profession, however it might have been 

 argued upon, as an assumed fact, by Commissioners and Boards of Sewers. 



The discussion was closed by the Dean of Westminster giving an example 

 of the urgency for engineers becoming geologists; and on Mr. Uendcl stating 

 that the clay at Leith was so hard as to require to he blasted, and yet that, 

 when exposed to a small current of water, was completely dissolved within a 

 fortnight, the rev. Dean at once explained it, as arising from the presence of 

 a multitude of minnte particles of mica, whose non-adhesive properties pro- 

 duced the speedy disintegration of the mass. This was admitted to be the 

 fact, and had been observed and allowed for by the engineer in the construc- 

 tion of the works. 



Nov. 27.— JosFiDA Field, Esq., President, in the Chair. 



The paper read was a " Description of the Old Southend Pier-head, and 

 the e.vtension of the pier ; with an inquiry into the nature and ravages of 

 tlie ' Teredo Navalis' and tlie means hitherto adopted for preventiny its 

 attacks.'' By Mr. John Paton. 



After describing the form of construction f the old pier-head, and 

 showing ihe adoption of copper sheathing for protecting it from decay, and 

 the inipurlunt cousideralious involved iu the attempt to preserve marine 

 structures, the paper explained Ihe ravages committed by marine worms 

 ( Teredo Navalis, Lymnoria Terebrans, and others) on the piles, both above 

 and below the copper sheathiug. Tins sheathing exieuded from the top of 

 the mud to three feet above low water-mark ; the worm destroyed the 

 timber f'rom two feet b' low the surface of the mud, to eight feet aliove low 

 water spring tides, and, in fact, out of thirty-eight lir timber piles, and 

 various oak piles, not one remained perfect, after beiug up only three years 

 indeed, some were entirely ealen through. 



A general outline of the extension ol the pier, and a minute description; 

 of the pier- head, were tlieu given, showing the means adojited by the us 

 of iron piles, aud by scupper-nailing the inner piles, to preserve the struc- 

 ture from decay. The greater portion of the extension of the pier, the 

 length of which was one mile, as well as the whole of the pier beail, we 

 constructed of square, hidlow, iron piles, aud scupper-nailed feniler piles ; 

 the iron piles being foiced to a depth of from eiglit feet to sixteen feet, by 

 pulling them backwards and forwards with ropes attached to them, aud 

 not by driving in Ihe usual inaiiuer ; they were then tilled with gravel and 

 concrete to w iiliin five feet of the top, aud the fir piles to sustain the super- 

 structure were fitted into them. The pier-head was constructed with forty 

 cast-iron piles, and twenty fender piles, nailed from five feel below the bed 

 of the sea to eight feet above low water; its greatest height was Iweulj- 

 li\e Icet above low water spring tides. 



The paper llien entered into an investigation of the nature and opera- 

 tii>ns of the Teredo Navatis, and showed, as a remarkable peculiarity, that 

 no ebeiiiical means bad hnherto prevriited wood from being destroyed by 

 ihese animals and lUe Lymnoria Terebrans, whose deslruclive pov^ers were 

 likewise noticed, aud as haviug peuetruled between ihe copper sheathiug 



