To cross a stream, street or valley (in which the delay brought on by a flight of locks at either facet could well be unacceptable) the valley is often spanned by a navigable aqueduct – a well known illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO https://musicainfantil00097.blogs-service.com/68057311/5-tips-about-urso-fofo-you-can-use-today