19 ARCHITECTURAL CONTRIVANCES; PROPS; PIT PROPS FOR USE IN MINES; FRAMES; SUPPORTS; LININGS; SHEETING; JOINTINGS; PANELLING; CASTINGS; BUILDING MATERIALS;NON-METALLIC BUILDING MATERIALS FOR USE IN MINES; PIT WOOD; MINE TIMBER; NATURALAND ARTIFICIAL STONE, CEMENT, LIME, MORTAR, PLAST ER AND GRAVEL; PARTS, ACCESSORIES, FITTINGS AND COMPONENTS FORTHE AFOREGOING