Solid residue remaining after certain types of coals are heated to a high temperature out of contact with air until substantially all components that easily vaporize have been driven off. The residue is chiefly carbon, with minor amounts of hydrogen, nitrogen, sulfur, and oxygen. Also present in coke is the mineral matter in the original coal, chemically altered and decomposed. The gradual exhaustion of timber in England had led first to prohibitions on cutting of wood for charcoal and eventually to the introduction of coke. Thereafter the iron industry expanded rapidly and Britain became the world's greatest iron producer (seeAbraham Darby). The crucible process (1740) resulted in the first reliable steel made by a melting process. Oven coke (about 1.5–4 in., or 40–100 mm, in size) is used in blast furnaces to make iron. Smaller quantities of coke are used in other metallurgical processes (seemetallurgy), such as the manufacture of certain alloys. Large, strong coke, known as foundry coke, is used in smelting. Smaller sizes of coke (0.6–1.2 in., or 15–30 mm) are used to heat buildings.