To cross a stream, street or valley (where the hold off due to a flight of locks at both facet can be unacceptable) the valley might be spanned by a navigable aqueduct – a famous illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Entire world Heritage https://canal-infantil11098.blogaritma.com/35265228/details-fiction-and-canal-infantil