106 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[April, 



portion of the piles were cut off on both aides, to prepare them for the sup- 

 port of the centres; and after the horizontal wedges weie fixed on tlie 

 heads of tlie cofTcrdani piles, on the .'iOth Sf-ptetiiher the first rih was set up 

 by means of large sheer poles and powerful hoisting tackle, and by the 10th 

 Novemher, the whole ten rihs were placed. 



When the masonry of the second pier was sufficiently advanced, the cen- 

 tre, which had been framed in the I'le of Dogs, was floated up the river, 

 and being hoisted upon a large duuble barge, was raised into its place by 

 means of screws, assisted by the tide. The colferdam of the third pier liad 

 by this time advanced, and soon afterwards that of the fourth pier, wlien it 

 became necessary to provide njore water-way by removing the pier between 

 the fifth and sixth locks of the old bridge, and forming a wooden tressel 

 frame of whole timbers for the traffic to pass. This was performed at the 

 cost of 4.'8000, by demolishing one half of the arch at a time, after which 

 the pier helow was taken away 4 feet below low-water mark. By the 4th of 

 August, 1827, the first arch was completed ; by the end of the year the 

 second arch was keyed in, the foundation of the third pier completed, and 

 that of the fourth laid. In 1821. the water being pumped out of the north 

 aljutment dam, and the excavations made, the first pile was driven on the 1st 

 of February, and the entire founiiaticms completed on the 1st of March fol- 

 lowing; the masonry was then carried up to the springing of the arches. 



The first arch turned having now stooii the entire winter, the wedges were 

 struck 2 inches back on e.ich side, and the crown lowered f of an inch ; the 

 wedges were driven back 4 inches on the following day, when the crown 

 of the arch sank annther half inch. On the third day they were driven back 

 6 inches, when the crown of the whole arch was clear, and shortly after the 

 wedges were entirely driven back, when the soffite of the arch was accu- 

 rately examined, and found to have preserved its form entire, although it 

 had lowered IJ inch. 15y this time the centres of all the other arches were 

 placed, and the masonry considerably advanced: in 1829 and 1830 the cen- 

 tres of the middle, fourth, and fifth arches were shifted back, and when re- 

 leased of their load, the middle arch sank 2J inches, the fourth 2J inches, 

 and the fifth 1| inch. 



The centre arch is 152 ft. span, and rises 29 ft. 6 in. above Trinity House 

 water mark; the arches en either side span 140 feet, and rise 27 ft. 6 in. 

 above the same line, and the abutment arches span 130 feet each, and rise 

 above the same line 24 ft. G in. The entire water way being G92 feet, the 

 total length of the bridge 1003 feet, its width from out to out 56 feet, and 

 its height above low water 60 feet. The two centre piers are 24 feet in 

 thickness, and the two others 2 feet less. 



The general depth at which the foundation of the piers is laid below low 

 water is about 29 ft. 6 in., and the total quantity of stone used in construct- 

 ing the bridge and its abutments was 120,000 tons ; the number of piles of 

 20 feet ill length under the piers and their abutments whs 2092, and the 

 total number for the cofferdams 7708. There were four sets of timber cen- 

 tres, each weighing on an average 800 tons. The amount of Messrs. Joliflfe 

 and Bank's estimate for the bridge alone, including an extra set of centres, 

 was only £423,081, 9s. 2d. The bridge was opeued to the public ou the 1st 

 of August, 1831, with great pomp, after having been in progress seven 

 years and three months. ' 



The engrLivings are accompanied by tlie contract specification, from 

 which we make the following extracts (See Plate VIII.): — 



The cofferdams of the abutments were of a circular form, and those of 

 the piers of an elliptical form, as shown in fig. 5, Plate VllI, composed of 

 two rows of Baltic timber piles, not less than 12j inches square, five feet 

 apart, connected together by three rows of double whole timber waleings ; 

 the top of the piles 5 feet above Trinity House water mark ; there was also 

 a third row of piles placed 6 feet from the second row; the heads were level 

 with half tides, or 7 feet below Trinity House water mark ; the spaces be- 

 tween the piling was filled with tough, well beaten clay, thoroughly puddled ; 

 the piling, it will be seen by the engraving, was well secured by diagonal 

 struts, besides wrought iron tie-bolts. 



FoMni/a/ion (Fig. 2). — The platforms of the abutments were laid 34 ft. 

 6 in. below Trinity Huuse water mark in the front, and 34 ft. 6 in. at the 

 back; the two side piers 40 feet, and the middle piers 43 feet; over the 

 whole surface, piles of elm, fir, or beech, 12 inches diameter and 20 feet 

 long, were driven into the clay 18 feet below the platform, in rows, 4 feet 

 asunder. All the piles were cut off to a level, and a space of 9 iuches deep 

 below the pile-head excavated and filled in with Kentish ragstone, well beat 

 down, and racked in with five parts of sharp gravel and one part of lime ; 

 after which, sills, 12 inches square, were spiked on the pile.heads trans- 

 versely ; the intervening spaces were filled in with brickwork, excepting at 

 the extremities, which were of stone. Above these sills there was laid 

 longitudinally another row of sills, spiked down to the first row of sills 

 witli 18-incli jagged spikes, and the spaces between filled-in level with 

 Bramley-fall stone. On these sills and stones was laid a platform of 6-inch 

 beech, elm, or fir planks, bedded in mortar, and spiked dowu with 12inch 

 jagged spikes, and upon this timber platform the masonry was built. Uound 

 the abutment, sheet piles inches thick and 18 fei't long, and round the 

 piers, 12 inclies thick and 20 feet long, were driven in ; the whole planed, 

 ploughed, and tiingucd at the edges. 



The masonry of the piers and abutments is formed on the exterior faces 

 with granite ashlar, 2 ft. 3 in. to 3 feet thick, with headers 5J feet long, and 

 the interior filkil iii with Bramley-fall, Painshaw, or Derbyshire stone. 

 T/ie Jive arc/ies are semi-ellipses, (he centre arch 152 feet span and 29 ft. 



6 in. rise ; the arch stones are of granite, 4 ft. 9 in. deep at the crown, and 



increasing to 10 feet at the springing. The two arches next the centre are 

 140 feet span and 27 (t. 6 in. rise; the arch stone 4 ft. 7 in. deep at the 

 crown, and increasing to 2 fec/t at the springing. The two side arches are 

 130 feet span and 24 ft. 6 in. rise ; the arch stones at the crown are 4 ft. 

 Gin. deep, increasing to 8 ft. 6 in. at the springing. All the stones are 18 

 inches thick at the intrados, and increase in thickness to the extrados, and 

 each arch has four connecting bars of wrought iron. 



T/ie centres consisted of eight ribs of Baltic fir, excepting the springing- 

 pieces, wiiich were elm and the wedges oak ; the covering of the centre was 

 of timber 7 inches thick, the spandrils over the piers are filled up solid 

 to the underside of tlie inverted arches, the depth of which is G feet in the 

 middle of the two centre piers, and 5 feet for tlie two side piers, 



Roadivay. — The interior spandril walls to carry the roadway are of brick, 

 three bricks thick, and on the top are stone corbels 18 inches deep, project- 

 ing 12 inches, over which are laid 9inch Yorkshire landings, and then the 

 whole surface of the bridge is covered with puddled clay 15 inches thick ; 

 over this, broken stone 12 inches thick, is laid ; and then granite paving, for 

 the footpaths and road. 



Next mouth we shall resume our review of this valuable work ; and 

 in closing our present notice, we most strongly advise our professional 

 readers to procure the work itself. 



A Treatise on the Principles relating to the Specification of a Patent 

 for Invention. By William Spence. London : royal 8vo. V. and 

 R. Stevens and G. S. Norton. 



The abstract conception of a patent Is perhaps one of the simplest 

 of legal ideas. The jealousy with which property is guarded in all 

 civilised states, aud especially in this country, takes cognizance not 

 merely of each individual's right of possi'ssiou to his goods, chattels, 

 and estate, hut even of his claims of peculiar advantage derived from 

 his ingenuity and contrivance, especially when his exertioas tend to 

 promote the general interests of the community. The poet who ex- 

 alts the moral and intellectual condition of his countrymen, and the 

 mechanist who enlarges their amount of physical happiness, have 

 equally a reward secured to them by the law of the land ; the pub- 

 lisher who pirates a copyright, or the manufacturer who infringes on a 

 patent, are amenable to the same system of legal retribution that 

 guarantees to every man that which is his own. 



Simple and intelligible, however, as is this theory of patent right, 

 its application to individual instances is beset with innumerable dtlii- 

 culiies. The question immediately arises, what is the nature of those 

 claims that demand the protection of a patent ? I» it sufficient that 

 the claimant should meiely have discovered some new and useful 

 principle, or must he, by an actual invented mode of application, have 

 shown how that principle is to be rendered available? To take an 

 example — would the first person who discovered the mechanical 

 power cf steam have been entitled to a patent unless he had likewise 

 invented a steam engine ? To this the reply is easy. A patent is the 

 remuneration which the State accords to an individual for having 

 realised or done something useful — not for having merely projected it. 

 For the man who discovers a principle without applying it, cannot be 

 said to have benefited his species ; so fur as he hiinselt is concerned, 

 his discovery is useless — he lacks either industry or talent to turn his 

 knowledge to account ; all he has done has been to onl.irge the means 

 of usefulness ot other men, and to ihem, not to him, is the credit due 

 of all that may result from the opportunities he h is art'orded them. 

 Tiie laws observed by Kepler, in his hands, might lor ever have re- 

 mained barren isolated facts, had not Newton applied them, and thus 

 given value to what previously were worthless details. 



It is clear then that patents are only due for inventions, whether 

 thev be modes of c.irrying out new and useful principle.'*, or improve- 

 ments on the methods of carrying out old and recognised principles, 

 rile next question that presents itself has reference to the absolute 

 originality of the invention. Suppose an invention to have been made 

 and not distinctly announced, nor so widely promulgated us to have 

 been generally known, and suppose that a discerning individual, having 

 bv some means become acquainted with this invention, had discovered 

 its merit, has he a right to a patent? Or suppose that another indi- 

 vidual, without having been aware ot its previous existence, had, so to 

 speak, re-invented that invention, can he claim a patent i The answer 

 to these questiuiis involves all that is complex in che law of patents ; 

 the degree of promulgation necessary to invalidate the claims for the 

 re-invention being so dillicult to determine, that only persons accus- 

 tomed to the nicciuis ot UiW, and versed in the precedents of the 

 courts, can in any particular instance venture to give an opinion. A-* 

 a guide for patentees through the tangled mazes of the law we know 

 no better work than Mr. William Spence's Treatise ou the Specilica- 



