Victorian illustration to download showing a gun barrel factory. Workmen hammer a gun barrel to weld the edges together. Behind them is a glowing furnace. The bars of metal formed by the steam hammer (see ST216) have been heated, rolled into sheets, and smaller sheets cut to size. Each sheet has been heated again and rolled into a tube, and a mandril (bar of iron) has been inserted in the tube. Now the three workmen hammer the heated tube to weld it together.