410 071 the Methods of laying 



though loaded with the pier, specifically lighter than an 

 equal bulk of water. After each pier was erected, the sides 

 of the box served again for the boxes of the other piers: 

 the pier was sunk and raised after the same manner as be- 

 fore described : there are not any piles under the piers of 

 Westminster bridge; aiid only one of ilie foundations was 

 found incapable of supporting its charge. Mr. Mylne, in 

 the erection of Blacktriars bridge, adopted the same method 

 as Mr. L:ibelye did at Westminster bridge in regard to the 

 caissons : but he piled the foundations, and by a machine 

 cut the piles off level with the bed of the river. In con- 

 templating the conspicuous irregularities; in the latter bridge, 

 much advantage does not appear to have been gained by 

 this extra expense, admitting the natural foundations to 

 have been the same, which it is understood was the fact. 



The practice adopted in the middle ages, probably from 

 the time of St. Benezet the shepherd of Avignon, in thft 

 twelfth century, the first superior of the order of hospi- 

 tallers called Pontitlces, as at the bridges of Avignon, St. 

 Esprit, Lyons, London, York, Newcar-tle, Rochester, fee. 

 until modern limes, was to drive piles in the bottom of the 

 river in the site of the intended pier, and then to cut them 

 off a little below low water: the interstices were then 

 filled with stone and strong cement ; upon the piles they 

 laid a grating of timber boarded with thick boarding, which 

 was the floor to receive the pier j the workmen taking ad- 

 vantage of the times of low water until the pier had risen 

 to the level of high-water mark : this method is of the 

 purest simplicity, nor does it require the aid of any ma- 

 chinery beyond a pile engine. The foundation of the 

 piers of London bridge, as appeared from the pier which 

 was taken down when the two small arches were converted 

 into one, was formed of a quadruple row of piles driven 

 close together on the exterior of the site of the pier, form- 

 ing a case to receive the stone and cement : it was not as- 

 certained whether there were piles in the heart of the pier ; 

 for as soon as the exterior piles were taken out, the great 

 force of the water cleared away the remainder, which was 

 driven down the river. 



With a view to protect the piers of London bridge, there 

 have been constructed round them what are called starlings: 

 a starling;is an inclosure of piles driven close together into 

 the bed of the river, and tied together and secured by hori- 

 zontal pieces of timber, and the space within them is filled 

 with chalk, gravel and stone, so as to form a defence to the 

 internal piles upon which the stone piers are erected. 



It 



