To cross a stream, street or valley (exactly where the hold off a result of a flight of locks at possibly facet could be unacceptable) the valley can be spanned by a navigable aqueduct – a famous instance in Wales will be the Pontcysyllte Aqueduct (now a UNESCO World https://ursofofo90009.boyblogguide.com/36047477/musica-infantil-for-dummies