To cross a stream, highway or valley (wherever the hold off a result of a flight of locks at either side can be unacceptable) the valley might be spanned by a navigable aqueduct – a popular instance in Wales is the Pontcysyllte Aqueduct (now a UNESCO World Heritage Website) https://musicainfantil89876.topbloghub.com/43496968/the-best-side-of-urso-fofo