To cross a stream, highway or valley (in which the delay due to a flight of locks at possibly side can be unacceptable) the valley may be spanned by a navigable aqueduct – a well-known illustration in Wales is definitely the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage Web-site) https://urso-fofo78887.livebloggs.com/43655665/the-canal-infantil-diaries