To cross a stream, street or valley (exactly where the hold off caused by a flight of locks at both facet could be unacceptable) the valley may be spanned by a navigable aqueduct – a well-known instance in Wales will be the Pontcysyllte Aqueduct (now a UNESCO Planet Heritage https://urso-fofo79887.blogrenanda.com/43684512/details-fiction-and-canal-infantil