John MacCulloch's ‘Millstone Survey’ and its consequences

During the Napoleonic Wars there was a shortage of suitable millstones for the British Ordnance gunpowder mills. John MacCulloch spent five summers searching Western Britain for a source of non-siliceous limestones to be used as gunpowder millstones. His search was authorized by the Board of Ordnance, which also paid all his expenses.

By 1812 MacCulloch had found suitable limestones in Sutherland, Skye, and at Glen Tilt, but the Board of Ordnance were unable to exploit any of the sources until 1815 when unsuccessful quarries were opened on Skye. After the defeat of Napoleon at Waterloo the British millstone project was abandoned. The military objective of the millstone survey was not achieved, but MacCulloch learned much about the geology of the older rocks of Britain and he built a reputation as an expert geologist through the papers he submitted to the Geological Society of London.