The bridge was built on piles, and must have been solidly constructed, for although it needed from the first a great deal of cobbling, and underwent much alteration, it survived almost to our own day. It consisted of twenty arches, nineteen of stone, and one of wood--the drawbridge. By this drawbridge was the tower or storehouse, upon which the heads of traitors were set up. This became decayed, and was taken down in April 1577. The heads were removed and set on the gate at the Bridge-foot towards Southwark. On the 28th August Sir John Langley, Lord Mayor, laid the first stone of a foundation for a new tower, in the same [Illustration: Old London Bridge from St Olave's Church.] place, which tower was finished in September 1579.[86] The great wonder of the bridge was the beautiful wooden structure, called Nonesuch House, which stood on the seventh and eighth arches from the Southwark side, and gave its name to the Nonesuch lock. The great weight of the buildings caused occasional sinkings and a general insecurity. In 1481 it is recorded that a block of buildings toppled over into the river. In 1633 a fire swept from one end of the bridge to the other, and many of the houses were destroyed, which were not rebuilt. In 1757-1758 all the remaining houses were cleared away in order to make the structure more secure. The bridge was one of the chief sights of London, and a great deal of history has grown up about it, but it would require a volume to do justice to these circumstances. One of the most curious of these was the duel between Sir David Lindsay, Earl of Crawfurd, and John Lord Welles (fifth Baron), Ambassador at the Scottish Court in 1390. Lord Crawfurd chose the place, and, furnished with a safe conduct from Richard II., came from Scotland to London for this special purpose. The duel took place in this apparently inappropriate locality in the presence of a great concourse of sightseers.