How a Mercury Barometer Works - Diagram & Explanation #23282 (License: Personal Use)

This technical illustration depicts a traditional mercury barometer, where atmospheric pressure acting on the mercury reservoir forces mercury up a sealed vertical glass tube. The height of the mercury column-measured against a calibrated scale in millimeters or inches-indicates current air pressure; the valve (labeled A) allows for calibration or maintenance. The U-shaped reservoir ensures consistent reference level and minimizes errors from thermal expansion.

Used in educational materials, meteorology guides, and physics textbooks to explain atmospheric pressure measurement principles; targets students, educators, and weather enthusiasts seeking foundational understanding of barometric instruments.