To cross a stream, road or valley (in which the delay caused by a flight of locks at possibly aspect can be unacceptable) the valley may be spanned by a navigable aqueduct – a famous illustration in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Planet Heritage Site) https://alexisrbgjn.snack-blog.com/37201063/5-easy-facts-about-musica-infantil-described