To cross a stream, highway or valley (where by the delay brought on by a flight of locks at either facet could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a well known instance in Wales may be the Pontcysyllte Aqueduct (now a UNESCO https://urso-fofo44332.bloggosite.com/44407857/helping-the-others-realize-the-advantages-of-musica-infantil