The waterway of the Thames was obstructed by the bridge, which formed a sort of lock to keep the waters in the upper portion of the river. The widest of the arches was 36 feet, and some were too narrow for the passage of boats of any kind. The resistance caused to so large a body of water on the rise and fall of the tide by the contraction of its channel produced a fall or rapid under the bridge. 'With the flood-tide it was impossible, and with the ebb-tide dangerous to pass through or shoot the arches of the bridge.' In the latter case prudent passengers landed above bridge, generally at the Old Swan Stairs, and walked to some wharf, generally Billingsgate. In 1428, according to Stow, the Duke of Norfolk was like to be drowned passing from Saint Mary Overy Stairs through London Bridge. His barge was overset and thirty persons drowned. In _A Chronicle of London_ (edited by Nicolas) we read 'as God wolde, the duke hymself and too or iij othere gentylmen seeynge that myschief, leped upon the pyles and so were saved through helpe of them that weren above the brigge, with castyng down of ropes.' Many such accidents were constantly occurring, so that there was probably truth in one of Ray's Proverbs: 'London Bridge was made for wise men to go over and fools to go under.' That boats were frequently overturned is proved by Norden's View of London Bridge, in which boats, bottom upwards, fill the foreground. [Illustration: THE TOWER OF LONDON.] CHAPTER V _The King's Palace--The Tower_ The Tower of London has existed for over eight centuries, and long before the Conquest the site was occupied by a Roman fortification. It is the most time-honoured building in Great Britain, and probably the foremost building (not a ruin) in the world. With so much in London that is new, it is a source of the deepest pride to every Londoner that there is a relic of the past of unequalled interest, on whose walls are written the chief incidents of the history of England. The name has long been a puzzle, but Mr. Horace Round has explained it, and thus thrown a fresh light upon the study of Norman military architecture. There were two different kinds of fortified places during the mediæval period, viz., (1) the Roman 'castrum,' or 'castellum,' which survived in the fortified enclosure, and (2) the mediæval 'motte,' or 'tour,' which survived in the central keep. When the 'tour' coalesced with the 'castellum,' a name was required for the entire fortress. Sometimes the keep was added to the castle, and sometimes the castle to the keep. It was then a question which word should prevail,--'tour' (turris), or chastel (castellum). Generally, the word castle has prevailed, but the respective strongholds in the capitals of Normandy and England were the 'Tour de Rouen,' and the 'Tower of London.'[89] Gray alludes to the 'towers of Julius,' and Shakespeare's reference to the place is equally erroneous:--