 Cast-iron columns for buildings had the advantage of being extremely slender, compared with masonry columns capable of supporting similar weight.That saved space in factories, and so after the five-storey 1795 Ditherington Flax Mill with its internal structure of cast-iron proved the concept, it became ubiquitous in the multi-level mills of northern England, and then further afield in all kinds of industrial and multi-storey structures, up until about 1900.It was also useful in other kinds of buildings, for instance enabling architects of theaters, churches and synagogues to improve sight lines when supporting balconies, by eliminating or at least making the columns that supported the roof or balconies thinner.