To cross a stream, highway or valley (wherever the hold off caused by a flight of locks at both aspect will be unacceptable) the valley can be spanned by a navigable aqueduct – a popular instance in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Globe Heritage Website) https://beckettktycf.blogcudinti.com/37297015/not-known-details-about-urso-fofo