Outdoor Clock & Barometer Sets

Barometers

• Barometers are either mercury or aneroid. Both types measure air pressure. Mercury barometers contain glass tubes that contain mercury in a vacuum. As the pressure outside of the tube increases, mercury is forced up higher into the tube. As the air pressure decreases, the mercury in the tube lowers. Aneroid barometers use a thick, heavy spring that opens and compresses as the air pressure changes. The movement of the mercury or spring causes a hand or wand to move. Most decorative barometers will have words such as "sunshine," "rain," or "change ahead" to help you decipher the meaning of the movements.

Clocks

• Most outdoor clocks are quartz clocks that are powered by batteries. Some that are paired with a barometer may be powered by air pressure, much like the barometer. These are called "Atmos" clocks. They contain tubes in which gasses are trapped. As air pressure increases and temperature rises, the gas expands, compressing a coil. As the gas compresses, the coil relaxes. The constant motion of the coil winds the clock.

Use

• Set your barometer according to the atmospheric pressure readings as reported by the National Weather Service. These readings are usually adjusted for sea level. Stick and dial barometers will not give you a precise reading over 1,000 feet unless a custom, shorter mercury tube is installed. Still, the reading given will be able to accurately predict whether a storm is coming or if sunny skies will appear. If the arrow (or hand) moves downward, this indicates poor weather. If it moves up, or increases, fair weather lies ahead.

Styles

• True antique barometer and clock sets use mercury tubes and are normally too fragile to keep outdoors. Reproductions are a better choice. Carefully crafted reproductions are often works of art and are therefore expensive. Some clock and barometer sets are simply shaped and made out of sturdy, durable fabric rather than wood. These are usually aneroid and quartz and are powered by batteries. Such clock and barometer sets will withstand the elements well and are less expensive than their wood and glass counterparts.