To cross a stream, road or valley (where the delay caused by a flight of locks at either aspect would be unacceptable) the valley can be spanned by a navigable aqueduct – a famed instance in Wales may be the Pontcysyllte Aqueduct (now a UNESCO World Heritage Site) through https://stephenltydi.bloggerchest.com/37141803/the-smart-trick-of-musica-infantil-that-no-one-is-discussing