To cross a stream, street or valley (the place the delay brought on by a flight of locks at either side could be unacceptable) the valley might be spanned by a navigable aqueduct – a famed case in point in Wales may be the Pontcysyllte Aqueduct (now a UNESCO https://anime-training-simulator38259.wizzardsblog.com/37102308/the-smart-trick-of-musica-infantil-that-no-one-is-discussing