GOLDSCHMID-FORM POCKET BAROMETER, Swiss, late 19th century, signed “Th. Usteri-Reinacher, Zurich, N. 1856.” This beautifully constructed aneroid barometer is contained in a shaped pebbled-leather covered doubly-hinged case, and consists of a 1-7/8″ (19 mm) diameter lacquered brass drum with twin index arms reading against a 400 – 800 scale, readout magnifier, and rotating top with inset circular thermometer and silvered cylindrical scale divided every half unit from 0 to 50. Condition is fine throughout.
Invented by the instrument maker J. Goldschmid c. 1857, the device consists of a totally unconstrained evacuated chamber bearing only against a tension spring which extends to the readout window, with a second spring alignable by rotation of the calibrated disk above. The long thermometer permits temperature corrections. According to Middleton (The History of the Barometer, pp. 418 – 420) “It was a remarkable first attempt at a null instrument of this sort….”
Ask the Dealer
David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at www.etesseract.com, and can be contacted at firstname.lastname@example.org.