Antique Barometers

Galileo inadvertently started the 17th-century craze for barometers by speculating on the effects of water pumped high in a tube. His associate Evangelista Torricelli performed similar experiments with mercury. Although his Torricellian Vacuum of 1643 wasn't conceived to predict the weather, the effect of the atmosphere on the mercury was undeniable: As the atmospheric pressure fluctuated, so did the height of the mercury. The popular banjo-shaped case arrived on the scene in the mid- to late 18th century, created by immigrant Italian craftsmen in England.

JUST THE FACTS

What to look for: Makers' names, often engraved on English examples, can be found in books listing the date and place of their workshops. Barometer Makers and Retailers, 1660-1900, by Edwin Banfield, is an excellent resource. If the original gilding is worn or only slightly touched up, consider yourself lucky. Touch-up gold paint oxidizes dark and indicates the case has been tampered with.

Condition: If the barometer is in working order, never rest it horizontally, or the mercury will run out of the glass tube. Be sure to hang it absolutely level, and don't hang it where a slamming door could jar it. Resulting air bubbles in the mercury will distort the reading.

Price range: Depending on rarity and condition, most mercury barometers are priced in the $2,000 to $10,000 range.

NextTrestle Tables