To cross a stream, street or valley (the place the delay because of a flight of locks at either facet could well be unacceptable) the valley might be spanned by a navigable aqueduct – a famous illustration in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Planet Heritage https://canalinfantil95170.blogrelation.com/43496214/the-best-side-of-urso-fofo