To cross a stream, street or valley (exactly where the delay brought on by a flight of locks at either facet can be unacceptable) the valley might be spanned by a navigable aqueduct – a well known illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Planet https://canal-infantil12110.tblogz.com/rumored-buzz-on-canal-infantil-50442723