Invented in the late 17th century by Torrecelli, the Wheel barometer shows changes in air pressure readings from the column of mercury in the back of the instrument. These changes are transferred through a pulley wheel to the hand on the dial, showing Rain to Fair.
French barometers all work on the same principal, but are distinguished by their carved giltwood frames and decorative design.
The changes in pressure readings from the mercury column on a Stick barometer are shown directly onto the dial. The Fitzroy barometer has a paper chart showing the weather readings directly from the mercury column. Admiral Robert Fitzroy invented this instrument in the mid 19th century.
The invention in the mid 19th century of the Aneroid barometer by Lucien Vidie enabled all barometers to be made in smaller cases and even to be carried in the pocket. The pressure changes are recorded from a vacuum capsule through to the dial pointer. Barographs record weather changes on a weekly chart and give an immediate graph of the trend and forecast of pressure changes.
These include various other items such as thermometers, compasses and other scientific instruments.