To cross a stream, street or valley (the place the delay due to a flight of locks at either side could be unacceptable) the valley may be spanned by a navigable aqueduct – a popular instance in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Globe Heritage Site) https://musica-infantil46654.p2blogs.com/35828272/facts-about-urso-fofo-revealed