To cross a stream, road or valley (exactly where the hold off because of a flight of locks at possibly aspect can be unacceptable) the valley may be spanned by a navigable aqueduct – a well known instance in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Environment https://ursofofo85173.blogchaat.com/37295962/the-fact-about-musica-infantil-that-no-one-is-suggesting