▁stations . ▁ ▁Black hall ▁Bridge ▁ ▁The ▁line ▁cross es ▁the ▁White ▁Water ▁of ▁Cart ▁at ▁Black hall ▁Bridge . ▁This ▁was ▁originally ▁an ▁aqu ed uct , ▁the ▁River ▁Cart ▁Aqu ed uct , ▁which ▁had ▁been ▁built ▁for ▁the ▁Ar d ross an ▁Canal ▁between ▁ 1 8 0 8 ▁and ▁ 1 8 1 0 , ▁under ▁the ▁direction ▁of ▁the ▁f amed ▁civil ▁engineer ▁Thomas ▁T elf ord . ▁The ▁contract or ▁for ▁the ▁aqu ed uct ' s ▁construction ▁was ▁John ▁Sim pson ▁and ▁the ▁cost ▁of ▁construction ▁was ▁£ 5 , 4 4 0 . ▁It ▁is ▁a ▁fre estone ▁m ason ry ▁segment al ▁arch ▁of ▁ 8 8   ft   6 in ▁( 2 7   m ) ▁span ▁and ▁a ▁height ▁over ▁the ▁water ▁of ▁about ▁ 3 0   fe et ▁( 9   m ). ▁The ▁bridge ▁is ▁probably ▁the ▁longest ▁span ▁m ason ry ▁aqu ed uct ▁of ▁the ▁canal ▁age ▁on ▁a ▁British ▁canal , ▁and ▁one ▁of ▁the ▁world ' s ▁earliest ▁brid ges ▁to ▁carry ▁a ▁public ▁railway . ▁It ▁had ▁to ▁be ▁w iden ed ▁in ▁order ▁to ▁carry ▁the ▁double ▁track ▁railway , ▁the ▁line ▁also ▁cross es ▁the ▁bridge ▁at ▁a ▁slight ▁ske w ▁because ▁of ▁the ▁eas ing ▁of ▁the ▁sharp ▁canal ▁curv ature . ▁ ▁Oper ational ▁difficulties ▁Author ▁David ▁L . ▁Smith ▁rec ount s ▁an ▁an ec d ote ▁illustr ating ▁the ▁difficulty ▁of ▁working ▁fast ▁trains ▁over ▁the