This sight would once have been familiar to many people in areas of terraced housing around Sheffield’s industrial heartland, but might be a bit of a puzzle today. The odd shaped pots on the top of the wall are actually fired clay crucibles, used for making special hardened steel in small quantities. They were heated at huge temperature and the molten steel poured out for later use at fine quality tool steel (as in the vintage photo below.) A process invented in the city at the end of the C18th, it was not unknown for the crucibles, which were often hand made on site from special clay, to last a couple of firings after which they became too fragile and were discarded. Most would be broken up but workers would sometimes make off with a few and use them as shown, cemented into place for a decorative top to a wall. Each crucible also had a clay lid, and these were also used for wall toppings and often as path edging.
I’ve walked and driven past this spot for many years, but only thought to take a picture recently. All it takes is a new house owner to take a dislike and they’ll be broken up and replaced by some horrible imported stone from India.
You can still see the site of an early crucible furnace at the Abbeydale Industrial Museum in Sheffield. And yes, this is where the name for the Crucible Theatre in the city came from.