These two mercury barometers from old Casey station in 1970 are high standard Fortin barometers. Fortin barometers were developed by French scientific instrument maker Nicolas Fortin around 1800, and were the most accurate type available for well over 100 years.
The principles of the mercury barometer was discovered by Evangelista Torricelli, a student of Galileo in 1643.
The most well known type of mercury barometer is the Admiral Fitzroy storm barometer, developed by Admiral Fitzroy in 1860. Fitzroy was a pioneer of weather forecasting and better known as commander of the Beagle the ship that took Charles Darwin on his famous circumnavigation.
The Fiztroy barometer was designed to be cheap to manufacture and therefore able to be installed on ships and weather stations around Britain.
For more on barometers