To cross a stream, highway or valley (where the delay due to a flight of locks at both aspect can be unacceptable) the valley might be spanned by a navigable aqueduct – a renowned illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Entire world Heritage Website) https://felixrxdhj.blogolize.com/the-best-side-of-urso-fofo-76128946