What type of barometer uses mercury to measure pressure?

The correct answer is a mercury barometer, which is a specific type of barometer that employs mercury to measure atmospheric pressure. This instrument consists of a glass tube filled with mercury, which is inverted into a reservoir of mercury. The height of the mercury column in the tube changes in response to variations in atmospheric pressure; when pressure increases, it pushes the mercury column higher, and when pressure decreases, the column falls.

The mercury barometer is notable for its accuracy and sensitivity, as mercury is a dense liquid, allowing it to measure small changes in pressure more effectively than other types of barometers. This design has been historically significant in meteorology and remains a classical method for measuring atmospheric pressure even in the modern era, despite the availability of digital technologies.