2 1 6 7 / 4 2 - 4 4 ) ▁( online ▁catalog ue ). ▁ ▁Engineering ▁ ▁Although ▁similar ▁in ▁size ▁the ▁bridge ▁to wers ▁are ▁not ▁identical ▁in ▁design , ▁the ▁Cl if ton ▁tower ▁having ▁side ▁cut - outs ▁whilst ▁the ▁Le igh ▁tower ▁has ▁more ▁pointed ▁arch es ▁and ▁cham fer ed ▁edges . ▁Brun el ' s ▁original ▁plan ▁proposed ▁they ▁be ▁to pped ▁with ▁then - f ashion able ▁s ph in xes , ▁but ▁the ▁orn aments ▁were ▁never ▁constructed . ▁ ▁The ▁ ▁Le igh ▁Wood s ▁tower ▁stands ▁at op ▁a ▁ ▁red ▁sand stone - cl ad ▁ab ut ment . ▁In ▁ 2 0 0 2 ▁it ▁was ▁discovered ▁that ▁this ▁was ▁not ▁a ▁solid ▁structure ▁but ▁contained ▁ 1 2 ▁v ault ed ▁ch amb ers ▁up ▁to ▁ ▁high , ▁linked ▁by ▁sh aft s ▁and ▁t unn els . ▁ ▁Rol ler - mount ed ▁" s add les " ▁at ▁the ▁top ▁of ▁each ▁tower ▁allow ▁movement ▁of ▁the ▁ch ains ▁when ▁loads ▁pass ▁over ▁the ▁bridge . ▁Though ▁their ▁total ▁travel ▁is ▁min usc ule , ▁their ▁ability ▁to ▁abs orb ▁forces ▁created ▁by ▁chain ▁def lection ▁prevents ▁damage ▁to ▁both ▁tower ▁and ▁chain . ▁ ▁The ▁bridge ▁has ▁three ▁independent ▁wr ought ▁iron ▁ch ains ▁per ▁side , ▁from ▁which ▁the ▁bridge ▁deck ▁is ▁susp ended ▁by ▁eight y - one ▁matching ▁vertical ▁wr ought - ir on ▁ro ds ▁r anging ▁from ▁ ▁at