Vintage horseshoe compensated aneroid barometer by the firm of SB Shortland smith, circa 1940. This charming barometer features a horseshoe surrounding the barometer and is mounted on a wooden shield. The workings of the barometer are visible through the glass.
The aneroid barometer was invented about 1843. The name aneroid simply means the movement is without fluid. Mercury barometers preceded the aneroids. Mercury barometers were quite long and the scales measured in inches of mercury. This unit of measurement carried forward to aneroid barometers – the readings on a barometer are normally expressed in inches of mercury. Readings of 30.0 inches or higher suggest dry settled weather. Readings below 29.0 may suggest more unsettled weather.
The barometer has an indicating hand that responds to changes in atmospheric pressure, and a set hand that is manually set to measure change in the indicating hand. This is a compensated barometer, which means that the accuracy of the instrument is not influenced by changes in temperature.
Barometric readings do not represent today’s weather, but forecast weather that will arrive in about a day.