To cross a stream, road or valley (where by the delay brought on by a flight of locks at either facet will be unacceptable) the valley could be spanned by a navigable aqueduct – a renowned case in point in Wales is definitely the Pontcysyllte Aqueduct (now a UNESCO https://andersonsycim.blogpostie.com/58349695/not-known-details-about-urso-fofo