To cross a stream, highway or valley (where by the delay caused by a flight of locks at either facet could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a popular instance in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage https://reiddkptv.educationalimpactblog.com/58564271/musica-infantil-can-be-fun-for-anyone