Explanatory notes
… the earth’s crust (e.g., for cutting and breaking down rock, earth, coal, etc.; earth excavation, digging, … etc. (A) Coal or rock cutters for cutting or breaking down coal, ores, etc. They consist of a bar or disc fitted … forced out by pumping water into the barrel, thus breaking down the rock or coal. (G) Ploughs, strippers, etc ., …