To cross a stream, highway or valley (in which the delay attributable to a flight of locks at either side could be unacceptable) the valley can be spanned by a navigable aqueduct – a famed case in point in Wales is the Pontcysyllte Aqueduct (now a UNESCO Entire world https://cruzcwqmf.tkzblog.com/36851540/considerations-to-know-about-musica-infantil