To cross a stream, highway or valley (exactly where the hold off due to a flight of locks at either facet would be unacceptable) the valley may be spanned by a navigable aqueduct – a well known case in point in Wales will be the Pontcysyllte Aqueduct (now a https://urso-fofo91100.boyblogguide.com/36051277/canal-infantil-an-overview