An edge mill or a chilian mill is a mill

Mill (grinding)

A grinding mill is a unit operation designed to break a solid material into smaller pieces. There are many different types of grinding mills and many types of materials processed in them. Historically mills were powered by hand , working animal , wind or water...

 used for crushing or grinding in which stones roll around on their edges, on a level circular bed. It is used for milling ore and as an oil mill. Horse or oxen-driven versions were used in pre-industrial revolution America as tan bark mills to shred tree bark to derive tannins for the leather industry.