To cross a stream, highway or valley (where by the delay attributable to a flight of locks at either aspect might be unacceptable) the valley can be spanned by a navigable aqueduct – a well-known example in Wales is the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage Web page) https://judahuvofu.dsiblogger.com/70107754/top-musica-infantil-secrets