Complex sentence: The Cowles companies are remembered for producing aluminium alloy in quantity and for inventing the electric smelter, one of the first viable methods for extracting aluminium sometimes called the "Cowles process", the immediate predecessor of the Hall-Heroult process.
Split into simpler sentences: The Cowles companies are remembered for producing aluminium alloy in quantity and for inventing the electric smelter, one of the first viable methods for extracting aluminium. Sometimes called the Cowles process, the process used was the immediate predecessor of the Hall-Heroult process.