Fortin’s barometer is a type of mercury barometer named after its inventor, French scientist Jean Baptiste Joseph Delambre. It’s a precise instrument used to measure atmospheric pressure. Here’s how it works and some key features:

1. Mercury Column: Like all mercury barometers, Fortin’s barometer uses a column of mercury to measure atmospheric pressure. Mercury is chosen because it is dense and exhibits minimal adhesion to glass, ensuring accurate and consistent readings.
2. Glass Tube: The barometer consists of a long glass tube sealed at one end and open at the other. The tube is typically filled with mercury, and the open end is submerged in a mercury reservoir at the base of the instrument.
3. Scale: A scale, usually marked in inches or millimeters of mercury (Hg), is attached adjacent to the mercury column. This scale allows the user to read the height of the mercury column, which corresponds to atmospheric pressure.
4. Cistern: Fortin’s barometer features a cistern, a small reservoir of mercury located at the base of the instrument. The cistern provides a stable reference point for the mercury column, allowing for precise measurement of pressure changes.
5. Adjustment Mechanism: To compensate for variations in atmospheric pressure due to altitude or temperature, Fortin’s barometer is equipped with an adjustment mechanism. This mechanism typically consists of a screw or vernier scale that can be used to fine-tune the height of the mercury column.
6. Leveling Mechanism: Fortin’s barometer often includes a leveling mechanism to ensure that the instrument is positioned vertically. This ensures accurate readings by preventing any tilting or sloping of the mercury column.
7. Transportation Case: Fortin’s barometer may come with a protective case for transportation and storage. This case helps to safeguard the delicate glass tube and mercury column from damage.

Fortin’s barometer is known for its precision and accuracy, making it a valuable tool in meteorology, atmospheric science, and environmental monitoring. Its design incorporates features to minimize errors and provide reliable measurements of atmospheric pressure, which are crucial for weather forecasting, research, and various industrial applications.