Complex sentence: The real revolution in steelmaking only began at the end of the 1850s when the Bessemer process became the first successful method of steelmaking in quantity, followed by the open-hearth furnace.
Split into simpler sentences: The real revolution in steelmaking only began at the end of the 1850s. The Bessemer process was the first successful method of steelmaking in quantity, followed by the open-hearth furnace.