1. How formed:—Places where forests, woods, etc., growing, sank—covered with water bringing soil—rose again—vegetable remains hardened into coal.
2. Hence found in layers.
3. Mining:—shaft, galleries.
4. Dangers:—fall of roof; flooding; explosions of “fire-damp;” afterwards “choke-damp.”
5. Safety lamp.
Iron.
1. Iron ore found in many places, worked on coal fields; why?
2. To drive away sulphur roasted in kiln, or with layers of coal on ground.
3. Mixed with coal and lime and placed in blast furnace.