To cross a stream, street or valley (in which the hold off caused by a flight of locks at either facet might be unacceptable) the valley is often spanned by a navigable aqueduct – a popular instance in Wales could be the Pontcysyllte Aqueduct (now a UNESCO Earth Heritage https://musica-infantil88876.ttblogs.com/16879954/considerations-to-know-about-musica-infantil