To cross a stream, road or valley (exactly where the hold off a result of a flight of locks at possibly side would be unacceptable) the valley may be spanned by a navigable aqueduct – a renowned instance in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Earth https://energiasolar56778.bloggip.com/37232364/not-known-facts-about-canal-infantil