Sediments approaching to the culm type, with similar flora and fauna, were deposited in synclinal hollows in parts of France and Spain.
The principal exports are corn and other agricultural produce; the imports are coal, culm, timber and slate.
The only doubt arises from the existence of insect remains, referred to the order Coleoptera, in the Silesian Culm of Steinkunzendorf near Reichenbach.
The cost of filling has been greatly reduced by the system of flushing culm, sand, gravel and similar material, through pipes leading from the surface into mine workings.
Mine fires may sometimes be reached by bore-holes sunk for the purpose from the surface, and the burning workings below filled by flushing with culm and water.