CHAP. VI. 



SOUTHWARK BRIDGE 



189 



and iron work of the bridge were erected with great care 

 and completeness. The blocks of stone in the piers were 

 accurately fitted to their places by moulds, and driven 

 down by a heavy wooden ram. The least possible 

 quantity of finely tempered mortar was used, so that 



large bracket-pieces of timber and 

 wrought iron plates and nuts, so that 

 the whole could be firmly screwed up 

 and braced together. The piles were 

 well headed and shod with wrought 

 iron, and driven from 15 to 20 feet 

 into the solid bottom of the river. 

 On the outside 'of the two main rows 

 of piles there was another placed 

 six feet from the inner, and driven 

 to the same depth, but their heads 

 only extended up to the level of half- 

 tide. They were tied together with 

 horizontal braces and wrought iron 

 screw bolts, in the same manner as the 

 two main rows. The joints of all 

 were well caulked, and the space? 

 between the three rows were filled 

 with well-puddled clay, so as to be 

 completely impervious to water. On 

 each dam there was a trunk three 

 feet square, fitted with a valve, which 

 could be lowered or raised at pleasure, 

 so that the water could be let off to 

 the level of low tide, or filled at any 

 time, in the event of any accident oc- 

 curring in the building of the piers. 

 Hie abutment coffer-dams were con- 

 structed in a semi-circular form, and 

 consisted of two rows of piles of like 

 dimensions, similarly rammed be- 

 tween with clay to keep out the 

 water. The enclosed spaces were 

 ] tumped out by means of steam- 

 engines of 20-horse power. The en- 

 gines worked double pumps of 15 

 inches diameter by an arrangement of 

 slide-rods. When necessary, as at 

 the City abutment, where the soil 

 was more porous, an additional engine 

 with pumps was employed. By these 

 complete methods the water was kept 

 under until the foundations were got 

 in at the great depth we have above 

 stated. The piers and abutments rest 

 on solid platforms of piles, cills, and 

 planking about 2 feet 6 inches thick. 

 The piles, of fir, elm, and beech, 



20 feet long and 12 inches in dia- 

 meter, shod with wrought iron, were 

 driven in regular rows three feet 

 apart, until a ram of 15 cwt. falling 

 from a height of 28 feet moved 

 them downward only half an inch 

 at a blow. Their heads were then 

 cut off level; the earth and clay 

 removed from about them to the 

 depth of a foot, and the space filled 

 in with Kentish rag -stone, well 

 rammed and grouted together with 

 lime and gravel. Cills of fir, beech, 

 and elm, 12 inches thick and 14 

 inches wide, were then accurately 

 fitted and spiked to each pile-head, in 

 the transverse direction of the piers 

 and abutments, with wrought iron 

 jagged spikes 18 inches long and six- 

 eighths of an inch square. The 

 spaces between the cills were solidly 

 filled with brickwork, and another 

 row of cills of the same dimen- 

 sions, laid at right angles to those 

 below, was fitted and spiked to them 

 over each row of piles, in the same 

 manner as above explained. The 

 spaces were then filled with brick- 

 work ; the whole surface was covered 

 with a solid flooring of elm-plank 6 

 inches thick, well bedded in mortar, 

 and spiked down to each cill with 

 wrought iron jagged spikes 10 inches 

 long and five-eighths of an inch square. 

 It may here be observed, as to the 

 use of timber at this depth, that when 

 it is exposed to an equable degree of 

 moisture it is found almost imperish- 

 able timber having been taken up, 

 as fresh as when laid down, from 

 the foundations of structures laid in 

 water for more than a thousand years. 

 Besides, timber is found, better than 

 any other material, capable of dis- 

 tributing the pressure over the whole 

 surface, as well as binding all the 

 parts of the foundations together. 



