To cross a stream, road or valley (exactly where the hold off caused by a flight of locks at either aspect would be unacceptable) the valley might be spanned by a navigable aqueduct – a popular instance in Wales is the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage Web-site) https://zaneweknq.blogpayz.com/37285362/the-ultimate-guide-to-urso-fofo