To cross a stream, road or valley (where by the hold off because of a flight of locks at both facet might be unacceptable) the valley is often spanned by a navigable aqueduct – a well known illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Entire https://musicainfantil90987.oblogation.com/36162285/the-definitive-guide-to-urso-fofo