Autobiography of Sir John Rennie, F.R.S., Past President of the Institute of Civil Engineers / Comprising the history of his professional life, together with reminiscences dating from the commencement of the century to the present time.

by Sir John Rennie

The design consisted of five semi-elliptical arches, the centre being 150 feet span, the two next arches 140 feet span each, the two side or land arches 130 feet span each; the two centre piers were 24 feet thick at the springing, and the two side piers 22 feet each; the whole was to be built of the best grey granite. The width of the roadway was originally designed to be 48 feet, but was afterwards increased to 54 feet wide, at an extra cost of 46,000l.

It was intended by my father that the new bridge should be built on the site of the old one, which was to be pulled down in the first instance, and a temporary wooden one was to be built above it to accommodate the traffic whilst the new bridge was building. It was considered that as soon as the fall of 5 feet occasioned by the old bridge should be removed, the river would be restored to its natural state, and there would then be less difficulty and expense in making the cofferdams and founding the piers and abutments; the old approaches to the bridge would then be preserved, and thus a less quantity of valuable property would be required. The wish, however, of the Corporation to preserve the old bridge during the construction of the new one was so strong, that there was no possibility of resisting it. I therefore yielded to their desire, and agreed to build the new bridge immediately above the old one, and as near as practicable to it; notwithstanding, I felt at the time that there would be considerable difficulty, risk, and extra expense in so doing, on account of the great depth of water in which the piers must be founded, namely, 28 feet at low water of spring tides, and the strong current and fall through the old bridge both during the flood and ebb, particularly during the latter. It should be observed that the old bridge stood as it were upon a hill, the foundations of the piers being from 28 to 30 feet above the bottom of the river immediately above and below it, occasioned by the great fall and scour produced by the contracted waterway; thus it was necessary to secure the piers by large projecting starlings, and to throw considerable quantities of stone continually round them, in order to prevent the old bridge from being carried away. However, there was no alternative but to build the new bridge above the old one, and I accordingly set about taking every possible precaution in order to prevent accident.

As the loose stone thrown round the piers of the old bridge was continually washed into the holes immediately above and below, it was in vain to attempt driving the piles for the cofferdams of the piers until this stone was removed, which was done by dredging. The cofferdams for the piers were elliptical in form, this shape being the best adapted for resisting the strong current in which they were placed; they consisted of two main rows of piles each 14 inches square, each pile being properly hooped and shod with wrought iron, and driven 25 feet into the bed of the river. These piles were connected together in the horizontal direction by three rows of braces 15 inches square, namely, one at the level of the lowest tides, another at the level of half tide, and the third at the level of high water. At every 10 feet the two rows of piles were fastened together with wrought-iron bolts 2½ inches diameter, which passed through the horizontal braces or walings, as they are technically termed, and were secured outside and inside with additional wooden cleats 15 inches square and 8 feet long, so as to cover the joints where the main horizontal braces met; outside of these were large iron plates, and as the bolts were screwed at each end, they could be tightened up to the full bearing without crushing the timber. On the outside of these two main rows of piles was a third row of the same dimensions, and driven the same depth into the bed of the river at a distance of 6 feet in the clear from the two main rows, and connected together with a tier of horizontal braces, and to the two main rows of piles with bolts, cleats, and plates of the same dimensions as those already described. When the piles had been driven to their proper depth, and had been properly secured to each other as above described, the joints between every pile, which had been previously fitted to each other, were well caulked with oakum, and the outside joints were covered with melted pitch, so as to render them water-tight; the spaces between the three rows of piles were then filled with strong well-puddled clay.

In addition to the above three rows of piles, there was a fourth row on the inside, driven down in the form of a parallelogram, corresponding with the exact size of the foundation of the piers, and to the same depth as the outer piles. Every tenth pile, and those at the corners or angles, extended up to the level of low water. Upon the heads of these piles longitudinal and transverse braces were fixed across the inside of the dam, at the level of low water, half tide, and high water; so that the dam was braced internally and externally in every direction to resist the pressure of the water, like a well-made cask. There was a powerful steam engine, with the requisite pumps, attached to each dam, to remove any water which might either rise from the foundation or from the outside. Each dam was provided with a trunk secured by a valve 3 feet diameter, laid at the level of low water, so that in the event of any unusual pressure of water coming against the dam, these valves were opened, and the dam was then filled with water, and all mischief was prevented. The first pier cofferdam on the Southwark side was completed, the water pumped out, and the earth was excavated to the depth of 30 feet, going below low-water mark of spring tides; the bottom consisted of the stiff London clay. Piles, consisting of Baltic fir, elm, and beech, 22 feet long, and 12 inches diameter in the middle, properly hooped and shod with wrought iron, were then driven 20 feet into the solid ground, or until, with a weight of 12 cwt. falling 18 to 20 feet, they would not move above an inch at a blow. These piles were driven 3 feet 6 inches from centre to centre, both in the longitudinal and transverse direction. After having driven them, their heads were cut off and accurately levelled. The loose earth between their heads was then removed, to the depth of 12 inches, and the spaces filled in with stone bedded in concrete; all the rows of piles were then connected together in the transverse direction by Baltic fir sills or beams 14 inches square, well fitted to each pile head by jagged wrought-iron spikes 20 inches long and three quarters of an inch square, driven through the sills into the pile heads below; the spaces between the sills were well filled in with stone and brickwork; another row of sills was then laid in the transverse direction above the pile heads and spiked down to the lower sills in the same manner; the spaces between the upper sills were then filled in with stone and brickwork. The whole surface of the foundation was covered with elm plank 6 inches thick, closely jointed together and bedded in mortar, and well spiked down to the sills below with jagged spikes 10 inches long and half an inch square. Upon this platform the masonry was built, each course diminishing in length and width by a series of offsets 12 inches wide, until they reached the shaft of the pier, when it was carried up solid to the springing of the arches. The whole of the exterior masonry was of the best whitish-grey granite, and the interior stone was of the best hard Yorkshire grit stone from the quarries of Bramley Fall. The abutments were constructed upon piles and masonry of the same character as the piers.

The first stone was laid with considerable ceremony on the first pier cofferdam from the Surrey shore by His Royal Highness the late Duke of York. The dam was fitted up with great taste like an amphitheatre, with seats all round, the whole being covered at top with a handsome coloured canvas awning adorned with numerous flags of all nations. The Lord Mayor, assisted by the Aldermen, Common Councilmen, and Committee, with Mr. Jones, the Chairman, attended in great state, and everything went off well. After this pier had advanced nearly to the level of high water, one day whilst examining it, standing upon one of the cross beams, my foot slipped, and I fell headlong into the dam upon the top of the masonry; fortunately, my left foot caught in a nail in the beam, and I hung by it for a few seconds. This somewhat broke and changed the direction of my fall, and I pitched upon an inclined plank, upon which I slid until I struck my head against a stone; my hat deadened the blow; as it was, however, I was cut about the forehead and half stunned. The after effects of this fall were very serious; my whole system got such a severe shaking, that I did not recover thoroughly until nearly ten years afterwards, and I carried on my large professional business with the greatest difficulty. The works made satisfactory progress, and the centres for the first and second arches from the Surrey shore were soon fixed.

Each centre was composed of eight ribs, framed upon the truss principle, resting upon a continued series of wedges in one piece, laid horizontally and resting upon tressels or legs formed by the piles of the cofferdams, which had been cut off and levelled for that purpose. The mode of setting and fixing the ribs was the same as that adopted at the Waterloo and Southwark bridges. A large lighter was constructed especially for this purpose. In the centre was placed a strong framing, which rested upon eight screws, four in each row, working in a strong cast-iron box, to which levers were attached, by means of which the screws and framing above them could be gradually raised and lowered at pleasure; at one end of the framing there was an upright scaffold. The centres, I have already said, consisted of eight main ribs framed together separately. As there was no room to frame these centres near the bridge, a special workshop and wharf were provided by the contractors at Millwall, in the Isle of Dogs; when ready they were launched in one piece, from a properly-prepared platform, into the river, and towed to the Southwark end of the bridge, where the lighter, with its apparatus of powerful sheers, crabs, and tackle, was in readiness to receive them; by these means they were gradually hauled up an inclined plane, and then raised upright upon the platform, supported by the frame and screws beneath, and firmly braced to the scaffolding in the lighter; two centre frames were thus placed upon it at one time, and adjusted by the screws to an extra height of 2 feet, so as to allow for any deficiency in the rise of the tide. Two ribs having been placed upon the framing, the lighter was hauled off from the shore and placed in front of the opening in which the centre was to be, the lighter being moored 100 yards from it, about half an hour before high water; upon the turning of the tide it was gradually allowed to float down with the ebb current to its place. By the time that the lighter with the centre ribs arrived in its exact position there was always 2 feet to spare, in order to allow for any deficiency of the tide; as the tide fell the two ribs were securely deposited in their places upon the framing and wedges below them. It should be observed, that upon the wedges there was an additional framing so as to reduce the weight of the main ribs of the centring. When the main ribs had been deposited upon the framing wedges, they were securely braced together until the whole number of ribs required for each centre was fixed, when they were all braced firmly together longitudinally, transversely, and diagonally. This mode of fixing centres for arches of any span was most successful and economical, and I believe that my father was the inventor of it, if it may be termed an invention. My excellent and talented friend, the late Robert Stephenson, adopted the same method for fixing the tubes of the Conway and Menai Straits bridges. He told me that he was not aware that my father had proposed it before him; but in the ‘History of the Britannia and Conway Bridges,’ edited, I believe, by the present Mr. Edwin Clarke, who was employed under Mr. Stephenson at the Conway Bridge, it is expressly mentioned that my father had previously employed the same plan.[3]

But to return to London Bridge. The works proceeded successfully; the fifth or last arch on the City side was completed in 1829. The centres of the first, second, and centre arches having been removed, it was found that they had subsided only 3 inches each, which was the exact distance that had been allowed for, with an extra half inch for the centre arch. Upon examining the arches and piers after it was supposed that they had subsided, it was found that there had been an unequal sinking, that the two centre piers had subsided on the east side slightly more than on the west side. I was much puzzled at this, and could not for some time account for the difference. Three or four of the quoin arch-stones of the second arch from the City shore had been fractured for about 8 or 9 inches; this, however, was of no consequence, for it is always difficult in such large arches to get the workmen to bed the quoins accurately. The same thing had occurred in the Waterloo and other bridges; I was therefore led to investigate the subject more thoroughly during the construction of the new bridge. It was found that the cofferdams for the piers in several instances were made in front of the openings or arches of the old bridge, which could not be avoided. These dams necessarily still further obstructed the waterway through the old bridge; I therefore felt that it was absolutely essential to find relief for the ebbing and flowing tides, detained both by the old bridge and the cofferdams of the new bridge, and accordingly recommended that, on the south side of the main arch of the old bridge, which was only 80 feet wide, two arches should be thrown into one, and that the intermediate pier should be removed, by which means a single wide opening would be made facing the space between the cofferdams of the arch and the centre on the Surrey side of the new bridge, but the difficulty of doing this arose from the fact that the traffic over the old bridge could not be interrupted for a moment. I soon, however, found an expedient; I ordered that the requisite number of logs of the best Baltic fir timber 15 inches square should be prepared sufficiently long to extend over the two arches and piers of the old bridge which I proposed to remove. Having got these ready, I stopped up one half of the roadway, leaving the other half open for the traffic, and working night and day, I laid these whole timbers spanning the two arches to the adjoining piers close together, bolted them to each other, and secured them to a longitudinal bearer of the same dimensions imbedded in the masonry of the adjoining piers, so that the timbers which were to form the increased opening rested firmly upon them. Having done this, I removed the masonry of the intermediate arch by degrees from beneath the timber girders, placing a strong diagonal strut or support under each girder as I proceeded, at the same time connecting together all these diagonal struts. Having completed one half of the temporary arch or opening, the traffic was diverted over it, and the other half was completed in the same manner; the whole operation was accomplished within ten days, and the traffic was not stopped for one hour. The intermediate pier of the old arch was then removed entirely. As the work advanced to the fourth pier on the City side another similar opening was made. These alterations relieved the river materially, and enabled the works to be carried on much more securely, and greatly diminished the fall through the old bridge at low water. Nevertheless, there was increased scour against the dams where the openings were made, which occasioned the slight unequal subsidence before mentioned. The last or fifth arch was completed on the City side, January, 1829.

It has been mentioned that Lord Liverpool’s Government had always taken the greatest interest in the construction of new London Bridge, and gave the Corporation of London every support in their power, not only for the accommodation of the great traffic across it, but for the improvement of the Thames, which the removal of the old bridge would effect; and amongst the men most zealous in Lord Liverpool’s Government were the late Marquis of Salisbury, then Lord Cranbourne, and the late Earl of Lonsdale, then Lord Lowther; both these noblemen had considerable talent, and, fully alive to the advancing ideas of the day, were mainly instrumental in forwarding this great work. That amiable, able, and conscientious nobleman, the Earl of Liverpool, had succumbed to the effects of a paralytic stroke, and the Duke of Wellington was now Premier; he took the greatest interest in the promotion of London Bridge and everything connected with it; so that the Corporation of London, who had hitherto been radically inclined, or had rather been opposed to the Tory Government, turned rather Conservative than otherwise, and the Duke became most popular with them; he invariably, whenever he could, accepted their invitations to Guildhall and the Mansion House, and was always received by them with the greatest respect and attention. Richard Lambert Jones, the Chairman of the London Bridge Committee, was his particular favourite, and he always shook Jones by the hand, a favour which he did not accord to everyone.

At this time the bridge had made considerable progress towards completion, and the important question arose, what was the best plan for the approaches? It was originally intended, in order to save expense, that the old line of Fish Street Hill, on the City side, should be adopted, pulling down such of the houses on this line as might be necessary to make the incline not steeper than 1 in 30; but inasmuch as the great traffic of Upper and Lower Thames Street interposed materially with the main body of the traffic coming north and south, it became most important to consider how this might be avoided, and the old idea of making an arch over Thames Street was revived, and was favourably received by the London Bridge Committee; the question was accordingly referred by them to me. I had always felt that the old approach by Fish Street Hill was a very great difficulty; but, restricted as I was to the old line of approach, I felt that I could not get out of it without some pressing necessity; I was therefore glad to have the opportunity of reconsidering the subject, particularly when proposed by the Committee. It was quite clear, that in any case an arch over Thames Street to separate the great cart traffic of that quarter from the main coach and passenger traffic coming from the City, Southwark, and the northern and southern parts of the town, was absolutely necessary, and I should have proposed it myself in the first instance, if there had at that time been any chance of its adoption, and I am quite sure that my father would have done the same. But if it had been proposed to divert the traffic from the old line of Fish Street Hill at the first, it is most probable that it would never have been carried; I was obliged, therefore, to confine myself to the old approaches, leaving the future to develop itself. The Committee, however, having taken up the idea of an arch over Thames Street, I was only too happy to fall in with it; but as nothing could be done without the sanction of the Government, it was determined by the Committee to bring the subject before them at once; the more so, as it would require a much larger sum than originally calculated to make the approaches, for which the Committee had no funds, and a new Act of Parliament would be required. Plans and estimates were accordingly prepared for the new approaches, and submitted to His Majesty’s Government. The Duke of Wellington took the greatest interest in the subject, and investigated it to the fullest extent; he visited the place himself, he interrogated the Chairman of the Committee and myself most closely, and at length, being fully convinced that it was necessary, gave the consent of the Government, provided that the funds could be found. In order to meet this difficulty, the Committee proposed to increase the coal tax, which, with the necessary sinking fund, would pay off the whole sum necessary to make the new approaches, which were estimated at 1,400,000l., in a given number of years. The Government consented to this, and the requisite notices, plans, &c., were given and deposited in the month of November, 1828.

Early in 1829 the Bill was brought into Parliament, and was most strongly opposed by the great northern coal-owners, Lord Durham, Lord Londonderry, Lord Lauderdale, and others, as well as by a considerable body of Londoners, and after a hard fight the Bill passed the House of Commons and got into the Lords; but here the opposition was more violent and powerful than ever. The Duke of Wellington, however, having been thoroughly convinced of the necessity and justice of the measure, determined that it should be carried if possible, whilst the Opposition were equally determined to throw it out. The Committee accordingly met in the Painted Chamber of the House of Lords, and the extraordinary number of forty peers, including seven cabinet ministers, assembled, the Duke of Wellington being in the chair. The Opposition comprised, amongst others, Earl Grey, his son-in-law the Earl of Durham, the Marquis of Londonderry, the Earl of Lauderdale, &c. Such a committee upon a private Bill has never since been seen in the Lords, and perhaps never will be again. The brunt of the battle fell upon me; I was the leading witness, and had to establish the whole case. I never felt more nervous in my life; I was to be prepared upon all points to defend everybody else’s errors as well as my own. I knew there were several weak points, and though I had an excellent case upon the whole, I still felt the greatest difficulty about it; I knew also perfectly well, that if I broke down, my career as an engineer was ruined for ever, for the Government had pinned their faith upon me; I therefore had made myself thoroughly master of the subject, and determined to sink or swim with it. Mr. W. Montague, then surveyor to the City, was a very sensible, practical man, and of great experience in the valuation of property, and possessed considerable influence with the Corporation; but whether it was jealousy at my being so much younger than himself, or whether he thought the post of honour should have been given to him, I cannot say, but he did not act cordially with me. That very remarkable man, Richard Lambert Jones, the Chairman of the Bridge, with his usual tact and sagacity, at once saw this, and thought that if he was examined there might be some discrepancy which our enemies would take advantage of; he therefore, with the concurrence of his Committee, determined that I alone should fight the battle of the estimates, upon which the whole fate of the Bill depended. It was well, both for Montague and myself, that this course was taken; for Montague, when the first Bill of 1821 was carried, had made the surveys of the property to be taken for the approaches on both sides of the bridge, which was confined to 180 feet above the old bridge. This limit ought to have been taken in a direct line, at right angles to the old bridge; but unfortunately it was taken according to the line of the shore, which near the old bridge receded considerably, whilst the old Fishmongers’ Hall projected beyond it, making the direct line, if taken, as it ought to have been, at right angles to the old bridge, 20 feet longer than if measured according to the line of the shore. This difference of 20 feet rendered it necessary that old Fishmongers’ Hall should be removed, and negotiations immediately commenced between the London Bridge Committee and the Fishmongers’ Company with respect to the purchase of this piece of land. The Fishmongers’ Company behaved very fairly; they said that they did not wish to build a new hall, as the existing structure answered their purpose very well; but if they were compelled to part with this 20 feet of ground, they must build a new hall, which they did not want to do. However, as they had no wish to impede the construction of the bridge and approaches, they were willing to sell the strip of land on which part of their hall stood, namely, 20 feet in width, for 20,000l. 1000l. per foot at first sight appeared a very large sum, although at present it would be considered remarkably cheap. The Committee of the bridge, looking at the matter fairly, resolved to pay the Fishmongers’ Company the required sum in full compensation for everything, and the Fishmongers’ Company might, if they thought fit, build a new hall at their own expense. This agreement was then settled, provided that the Bill for making the new approaches by an arch across Thames Street should pass the legislature. Knowing this fact, I was very anxious that this error of Mr. Montague’s should not come out before the Committee of the House of Lords, as it was no doubt a great mistake, and if it had transpired, it might materially have injured our case. I determined, therefore, during my examination, to keep it out of view as far as possible; at the same time, if it was fairly put to me, of course I felt myself bound to give every honest explanation. Perhaps Mr. Montague was not anxious to be examined; anyhow, he was not, and the whole burthen fell upon me.