MARK SYKES / SCIENCE PHOTO LIBRARY MARK SYKES / SCIENCE PHOTO LIBRARY
Mercury steam pressure gauge. Artwork of a steam pressure gauge based on a mercury manometer design. The manual valve (left) was used to open the gauge to the steam in the engine, and the steam then pressed down on the mercury (black) in the u-shaped glass apparatus. The pressure was measured by the rise of the mercury on the other side of the tube. This is the same mechanism used to measure area pressure with a mercury barometer.
Model release not required. Property release not required.