John Southern ( 1758–1815) was an English engineer, son of Thomas Southern of

Derbyshire Derbyshire ( ) is a ceremonial county in the East Midlands of England. It borders Greater Manchester, West Yorkshire, and South Yorkshire to the north, Nottinghamshire to the east, Leicestershire to the south-east, Staffordshire to the south a ...

. In 1796 he and his employer

James Watt James Watt (; 30 January 1736 (19 January 1736 OS) – 25 August 1819) was a Scottish inventor, mechanical engineer, and chemist who improved on Thomas Newcomen's 1712 Newcomen steam engine with his Watt steam engine in 1776, which was f ...

co-invented the

Indicator Indicator may refer to: Biology * Environmental indicator of environmental health (pressures, conditions and responses) * Ecological indicator of ecosystem health (ecological processes) * Health indicator, which is used to describe the health o ...

, an instrument for measuring and recording the pressure inside a steam engine cylinder through its stroke. This data was crucial for assessing an engine's efficiency. Southern became a partner of the firm of Boulton & Watt in 1810. The use of the instrument was kept as a trade secret for a generation, only becoming public in the 1830s.

References

English engineers 18th-century English engineers People from Derbyshire 1815 deaths Year of birth unknown Year of birth uncertain {{England-engineer-stub