&i 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Feb. 



disrontinaed for a time, but recently to have been resumed. Rennie pro- 

 posed it for the foundation of the Penitentiary in 1811 ; Smirke and others 

 followed in the same track, and now the employment of concrete for the 

 foundations of buildings has become nearly universal, wherever it is ne- 

 cessary. 



lirick has been much used for bridges over canals and drains by Rennie, 

 and in railway bridges by Stephenson, Cnbilt, Locke, Uastrick, and 

 others; and, latterly, it has been carried to a far greater extent by Brunei 

 in his bridge across the Thames at Maidenhead, for the Gre.it Western 

 Railway. It consists of two semi-elliptical arches, each 130 feet span, 

 and rising 24 feet ; they are built wholly of brick, in Roman cement. 



Ruman Cement, discovered by Parker, in 17U0, is chiefly made from a 

 stone found on the shores of the Isle of Sheppy, near Sheerness ; it is 

 burnt in a kiln, and when ground into line powder, possesses the peculiar 

 property of setting hard immediately, although exposed to water, which 

 renders it very valuable in hydraulic works. It had been little used in 

 public works until it was adopted by Uenuie and others. It was exten- 

 siTely employed in the naval works at Sheerness and elsewhere, and is now 

 uoi\ersally employed in buildings w liere immediate induration or setting is 

 required, in order to prevent the action of water, or where any settlement 

 from insistent weight would be injurious. Latterly Roman cement has 

 been found at Harwich and other places. Aberthaw, Lyme, Barrow and 

 other limestones also possess valuable properties for waterworks. The 

 success of buildings depends materially upon the cement or mortar em- 

 ployed : and much has been done by Sraeaton, Rennie, and Telford, in the 

 selection of the best lime, sand, and other materials, iu combining them in 

 proper proportions for the respective parts of the works where they were 

 employed, and in the application of machinery for the more thoroughly 

 mixing up and incorporating the materials together. Great credit is also 

 due to Higgins, Pasley, Donaldson, Smith and Godwin for their valuable 

 experiments and treatises upon this important subject." 



Additional strength has been given to brick structures, by the introduc- 

 tion of bands of thin hoop iron between the courses ; this improvement was 

 lirst generally introduced by Sir M. I. Bruuel. 



Tunnels. 

 Subterranean tunnels have been much used in inland navigation, particu- 

 larly in the Duke of Bridgewater's Canal, some miles of which, at Wors- 

 ley, are made underground; in the Harecastle Tunnel, by Brindley, on 

 the Trent and Mersey Canal, in 1770, which was rendered more convenieut 

 by Telford, iu IS'iO, by adding anotlier parallel to it, of larger dimensions ; 

 in the Hudderslield Canal, where there is a tunnel 5280 yards long; in 

 the Braunston Tunnel, on the Grand Junction Canal, and many others : 

 allof these, however, have been surpassed by tlie Tunnel under the Thames, 

 at Rotherhithe, by Sir Isambard Brunei, which, for magnitude, bolduess 

 in the design, and ingenuity iu the means of construction, as well as the 

 extraordinary difficulties by which the work was attended, will long re- 

 jimin a lastijig monuiueut of the talents and perseverance of that celebrated 

 engineer. This extraordinary work was commenced in 1825 ; it consists 

 of two arched openings 1200 feet in length, 14 feet span each, 10 feet l 

 inches high, separated from each other by a pier 1 feet thick, having sixty- 

 four lateral arches of 4 feet span, to communicate between the main open- 

 ings, the whole being surrounded with massive walls. The external di- 

 mensions of the walls, iucludmg the openings, are 38 feet wide, and 22 

 feet high. It is approached at each end by a perpendicular shaft, 50 feet 

 diameter, and 80 feet deep; but the tunnel was intended hereafter to be 

 carried out to the surface f the adjoining streets, at such a moderate in- 

 cliuation that carriages could easily pass through it from both sides of the 

 river. The crown of the tunnel is about 10 feet below the bed of the 

 river. In order to carry into efl'ect this very difficult work, unusual means 

 and precautions were necessary. The ordinary wooden centre framing 

 scarcely presented sufficient strength and connexion for that purpose, 

 lirnnel accordingly invented a cast irou frame (which he termed a shield) 

 sufficiently large to embrace the whole width and height of the intended 

 structure, and divided into thirty-six compartments, each sufficiently large 

 for a man to work in, yet capable of being closed to prevent the access of 

 water when required ; the whole was impelled forward by powerful 

 screws, bearing upon the work behind, as it was hnished. Tliis ingenious 

 contrivance was perfectly successful ; and although the works were twice 

 stopped by the irruption of the Thames, nevertheless the apertures were 

 stopped by bags of clay and other materials, and the structure was con- 

 tinued with extraordinary perseverance uutil Uually completed and opened 

 to the public in 1843. The whole was constructed with bricks set in 

 Roman cement, and cased inside with the same material ; and it gives 

 e^ery prospect of permanence and solidity. 



A tunnel under the Thames had been previously proposed at Rotherhithe 

 by Trevelhick, and had advanced to some distance under the river, ^^llen 

 it was abaudoned ; also one by Dodd at Gravesend, which was scarcely 

 commenced. A tunnel was also carried to a considerable extent under the 

 Severn, at Newnham, but failed for want of funds. 



Tunnels form part of the works of almost every considerable railway, 

 and the art of coustriicling them with accuracy and expedition is now- 

 brought to great perfection. Amongst the most remarkable tunnels exe- 



* From tlie valuable researthes of ttitse authors it aiipears, tliat the hydraulic cemeuts 

 contain considerable jiortioiis ot silica autl alumina, and in eunic cases metaiic oxides ; 

 and, where natural liydraulic cements canuot be obtained, they may he l)roLluc«tl urU- 

 ficialli, by tile combluatiou «t' tliejc Insreicnlt Iu their proper proiiortioua. 



cnted upon railways, may be mentioned that at Kilsby, 2398 yards long, 

 on the Birmingham and London line, by Stephenson; that at Box Hill, 

 3195 yards long, on the Great Western Raihvay, by Brunei ; and that on 

 the Sheffield and Manchester line, 5280 yards long, by Locke. Seversil 

 others of great length are now in progress. 



Harbolt.s. 



In the construction of harbours, Smeaton, as already observed, had 

 pointed out the proper course, in his reports ou Lynn, Wells, Aberdeen, 

 Dundee, Dunbar, Port Patrick, Sandwich, Scarborough, Sunderland, 

 Workington, Rye, Dover, and others. Ramsgate harbour was originally 

 designed by Labelye in 1744; it had been partly executed by others, and 

 continued with little success through a tedious succession of years, with 

 various changes of plan, until 17 74, when it was placed under .Smeaton's 

 direction ; he soon saw the evil arising from the constant accumulation of 

 mud which threatened to fill it up, in consequence of there being no back- 

 water or scouring power to remove it. He therefore divided the harbour 

 into two parts by a cross wall ; the part next the shore formed a basin of 

 eleven acres, in which the water could be retained f.y means of a lock, 

 and discharged through powerful sluices in the cross wall into the oul£r 

 harbour at low water, and thus form an etfectual scouring power for re- 

 moving the mud. Here was the introduction of a new principle for the 

 maintenance of harbours, which is so difficult on an alluvial coast, operated 

 upon by the tides and currents ; and although previously in use on the 

 Continent, it is believed to be the first example of the kind in Great Bri- 

 tain. Smeaton afterwards continued the works, and introduced an im- 

 proved system of masonry ; in 1788, he founded the outer and inner walla 

 of the outer piers, below low water, by means of caissons or boxes of 

 wood, and so far unproved the diving-bell as to render it useful in carrying 

 on the operations, although he did not build with it , and about the same 

 time he used it for examining the foundations of the piers of Hexham 

 bridge, one of which had partially sunk. The late Mr. Rennie, who after 

 Smeaton's decease took charge of the works at Ramsgate, prohting by 

 what had been done, carried out the system to a greater extent, by enlarg- 

 ing the sluices and making them of cast iron, the old ones being of wood 

 and frequently out of repair ; a greater quantity of water could then be 

 discharged in the same time, when required, and thus act with greater 

 ellect ; or the discharge could be prolonged, according to circumstances. 

 The masonry also, which, although good for the early period at which It 

 was constructed, had become dilapidated, was rebuilt, where requisite. In 

 a much more substantial manner. The steam-dredging machine was also 

 applied to remove that portion of the mud which could not be effected by 

 the sluices. The diving-bell was afterwards perfected by Rennie, so as to 

 be perfectly manageable, and being suspended from a frame worked by 

 proper machinery, it could be raised and lowered, or moved laterally, in 

 any direction, with facility and promptitude, either according to the direc- 

 tions of the diver within the bell, communicated by meaus of signals, made 

 by striking the sides of the bell with a hammer, or given by the superin- 

 tendent above. All the operations for preparing a foundation, and aftei^ 

 wards laying the prepared blocks of masonry upon it, could thus be per- 

 formed with as much certainty below as above the water. Rennie first 

 used his improved apparatus in 1813 for rebuiiding the advanced East 

 Pier Head at Ramsgate Harbour, which was founded 17 feet below low 

 water of spring tides with complete success. The value of this invention 

 for submarine operations was now completely established, and he after- 

 wards employed it with advantage in founding the pier heads and outer 

 walls of Holyhead, Howth, and Sheerness Harbours, and other works 

 under his direction, and it is now generally adopted iu all similar circum- 

 stances. The diving-helmets and dresses, improved by Deane, Belhell, 

 Edwards, Seibe, and others, have also materially contributed to the suc- 

 cess of submarine operations. 



After Smeaton, numerous artificial harbours were designed and con- 

 structed, and natural ones improved ; amongst the former may be men- 

 tioned Holyhead, Howth, and Kiugsto«u ; at the latter there is a depth 

 of 20 feet at low water of spring tides, and an enclosed area of 250 acii« 

 at low water ; which is the largest harbour attempted in this country by 

 Renuie. Here and at Howth he substituted the flat slope for the upright 

 wall to resist the waves,* and introduced the plan of throwing down louw 

 blocks of rubble, or unhewn stone, for forming the main body of the pier«, 

 allowing the slope or angle of repose, at which the materials would lie, to 

 be formed by the sea. In his system of making low-water harbours, 

 which, up to that period, were almost unkuotvu la Great Britain, ha 

 adopted the plan of euclosiug the area by piers composed of several 

 straight arms or lengths, iutersecting each other according to particular 

 angles, instead of making them curved, which, in his opinion, only served 

 to increase the action of the waves. In asylum harbours, when prao- 

 ticable, as at Kingstown, he preferred making the entrance open to the 

 dangerous wind, thus rendering them more accessible for vessels iu dis- 

 tress; but in order to prevent the prejudicial eil'ects of any waves which 

 might roll into the harbours, he adopted the returning and inclined form of 

 entrance, by which means increased facility of entrance and departure 

 was also given. He also designed his harbours with a view to preserving 



the ' ■ ' ■ ' ' ■ ' '" ' ■' 



es 



e original depth, as far as practicable, which is a principle of the great- 

 t importance, and ought not to be lost sight ol'. The artificial harbours 



* Tliis system was latterly always adopted by Rennie and Telford In preferenee to the 

 upright wall, as beuig better ada|)ted to resist waves, and It lias been iuifunably buccesa- 

 (iii, wiiercver it liiu beea j;rui)erly cjirrieU into etf^t. 



