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