To cross a stream, road or valley (the place the delay brought on by a flight of locks at either facet might be unacceptable) the valley is often spanned by a navigable aqueduct – a famous case in point in Wales could be the Pontcysyllte Aqueduct (now a UNESCO https://canal-infantil34332.csublogs.com/44480114/the-fact-about-urso-fofo-that-no-one-is-suggesting