To cross a stream, street or valley (where the hold off due to a flight of locks at possibly side can be unacceptable) the valley can be spanned by a navigable aqueduct – a well known example in Wales is the Pontcysyllte Aqueduct (now a UNESCO Earth Heritage Site) https://musica-infantil88876.ttblogs.com/16879954/considerations-to-know-about-musica-infantil