LONDON BRIDGE was built somewhat to the west of the site formerly occupied by Old London Bridge, an antiquated stone structure, that was erected about the beginning of the 13th century, by Peter of Colechurch, who combined the professions of architect and priest : he died in the year 1205, and was buried in a crypt within the centre pier of the old bridge, over which there was a chapel dedicated to St. Thomas a Becket.
The contractors for the building of the new bridge, Messrs. Jolliffe and Bankes, under the superintendence of Mr. (now Sir John) Rennie, the engineer, drove the first pile of a coffer-dam for the south pier, on the 15th of March, 1824.
The general form of the dam was elliptical. Three rows of piles shod with iron, and many of them measuring between 80 and 90 feet, were driven into the ground, and after being bolted together by means of walings, the spaces between them were puddled with clay, &c.; wooden stays or props were also placed between the different rows of piles and the interior space of the dam, strongly truss-framed between longitudinal beams. This coffer-dam been completed, the first stone of the new bridge was laid by the then Lord Mayor of LondOn, in the presence of H. R. II. the Duke of York, on the 15th of June, 1825.
Piles of beech-wood were driven into the natural bed of the river, consisting of stiff blue clay, to the depth of about 20 feet ; two rows of horizontal sleepers, about a foot square, were laid on the tops of those piles, and these again were covered by a planking of beech, 6 inches in thickness; and on this flooring the foundations of masonry were laid. The same system was adopted for all the piers and abut ments.
The construction of centering for the arches was the next step in this great undertaking. Each centre was composed of ten frames, joined together on the principle of the diagonal truss—each frame rested at either end on a pile driven into the river. The ten frames were then boarded over with planks placed within 2 or 3 inches of each other. In con
sequence of a difference in size in the arches, it was necessary to have four sets of centres.
On these centres the arches were turned in the ordinary manner, and in the spandrels hanee-walls were built, longi tudinally, so as to oppose the thrust of the arches without overloading the haunches. On the top of those walls heavy blocks of stone were bedded, and on these were laid stone landings, upon which was placed a layer of tarras, and over that again, the puddling, on which the roadway was formed. The first arch was keyed in on the 4th of August, 1S27, and the last on the 10th of November, 1828.
The approaches on either side of the bridge were carried on arches over some of the streets running along the banks of the river. The arch over Thames-street, in particular, is worthy of attention, being very flat, having been constructed over the roadway and both the footpaths of Thames-street, and the centering for it had to be so made as to leave an uninterrupted passage for vehicles and pedestrians; it was entirely supported by struts ranged along the junction, between the carriage-way and footpaths, and the abutments of the arch ; on these the wedges were placed upon which the centering was made to rest.
The only alteration in the original plan of Mr. John Rennie, the engineer who designed the work, was the addition of 6 feet to the roadway, and an increased height of 2 feet in the abutment arches. The alteration in the width of the roadway was loudly insisted on by the public ; and the government ordered that the additional cost it would necessitate, should be met by a public grant to the amount of £42,000. The additional height in the side arches was proposed by the present Sir John Rennie, on whom the execution of the work had devolved on the demise of his father. This great undertaking was entirely completed on the last clay of July, 1831, after having been about seven years and a-half in the course of construction.