To cross a stream, highway or valley (wherever the hold off due to a flight of locks at both aspect will be unacceptable) the valley may be spanned by a navigable aqueduct – a famous case in point in Wales is definitely the Pontcysyllte Aqueduct (now a UNESCO Earth https://musica-infantil90998.aioblogs.com/89867362/the-ultimate-guide-to-urso-fofo