To cross a stream, street or valley (the place the delay brought on by a flight of locks at either facet will be unacceptable) the valley could be spanned by a navigable aqueduct – a well-known example in Wales is the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage Web-site) https://tysontchlp.blogdiloz.com/35969899/detailed-notes-on-musica-infantil