To cross a stream, street or valley (in which the delay a result of a flight of locks at possibly aspect can be unacceptable) the valley might be spanned by a navigable aqueduct – a well known illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Planet https://musica-infantil01099.blogadvize.com/45069090/5-essential-elements-for-musica-infantil