To cross a stream, road or valley (exactly where the hold off because of a flight of locks at both aspect will be unacceptable) the valley might be spanned by a navigable aqueduct – a popular instance in Wales will be the Pontcysyllte Aqueduct (now a UNESCO World Heritage https://paxtonclpvc.gynoblog.com/36142792/musica-infantil-can-be-fun-for-anyone