Complex sentence: Moses Austin started large-scale mining, at Potosi, originally known as Mine a Breton, and smelting, at Herculaneum; this lead was originally used as a roofing material.
Split into simpler sentences: Moses Austin started large-scale mining, at Potosi, originally known as Mine a Breton, and smelting, at Herculaneum. U.S. Geological Survey Scientific Investigations Report 2008--5140, Chapter 1 This lead was originally used as a roofing material.