To cross a stream, street or valley (in which the delay because of a flight of locks at possibly side would be unacceptable) the valley is usually spanned by a navigable aqueduct – a renowned case in point in Wales would be the Pontcysyllte Aqueduct (now a UNESCO World https://reiddkptv.educationalimpactblog.com/58564271/musica-infantil-can-be-fun-for-anyone