Read it through once

The subsoil in this particular cornfield (on Pennell Brae) lies upon the trap-rock formed by one of those gigantic lava-flows which cover that part of Renfrewshire. The whole district at that time must have been exactly like Vesuvius during the late eruption. Its scenery in this early miocene period consisted of glowing molten rock, accompanied by flames of fire, electrical storms, clouds of gas, dust, ashes, and superheated steam.