To cross a stream, road or valley (exactly where the hold off a result of a flight of locks at both aspect could be unacceptable) the valley can be spanned by a navigable aqueduct – a popular instance in Wales will be the Pontcysyllte Aqueduct (now a UNESCO World https://canal-infantil12109.thezenweb.com/5-essential-elements-for-musica-infantil-75344458