To cross a stream, road or valley (wherever the delay brought on by a flight of locks at both side will be unacceptable) the valley might be spanned by a navigable aqueduct – a popular illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Entire world Heritage https://musica-infantil66543.blog-a-story.com/18323012/indicators-on-canal-infantil-you-should-know