![](https://coimages.sciencemuseumgroup.org.uk/711/82/large_thumbnail_2023_0467__0010_.jpg)
![Calcined tap cinder called 'bull dog' when used for the bottom](https://coimages.sciencemuseumgroup.org.uk/404/622/medium_smg00093378.jpg)
Calcined tap cinder called 'bull dog' when used for the bottom of a puddling furnace, burnt in a kiln at Ebbw Vale, 1865, according to Barrows and Halls patent
Calcined tap cinder called 'bull dog' when used for the bottom of a puddling furnace, burnt in a kiln at Ebbw Vale, 1865, according to Barrows and Halls patent