Barometer, Mercury
Production date
1841-1842
Description
'Stick' barometer - long, narrow carcass made from dark wood (mahogany?). Long glass tube (filled with liquid mercury) runs vertically up the body - lower end stands in a cistern (hidden by a conical wooden cistern cover at base of barometer). The Upper end is sealed with a small vacume at the top (since the vacume gives no resistance any change in the air pressure causes the mercury to move in the tube). At the upper end of the barometer is a silvered metal plate which has "Dolland London" (the retailer) engraved at the top and an air pressure scale on the right hand side (in England the maximin range of variation in air pressure is approx between 27.5 and 31 in. thus most domestic barometers have a scale between 27 - 31 in). For improved accuracy these inches are subdivided into decimals and a small sliding vernier scale has been added on the left hand side (the vernier scale allows the reader to obtain a reading to a further place of decimals to an accuracy of 0.1in). Attached to the vernier scale is a pointer which can be set to the level of the mercury. The vernier is 1.1 inches long and is divided into 10 equal parts - these divisions are numbered downwards from the zero or pointer line. The vernier is adjusted manually via a small round turning knob just below the scale plate. Glass cover protects the plate. In addition to the scales there are the following engraved weather indicators "FAIR CHANGE RAIN". Note adhered to stem below plate reads: "NOTE: This barometer was purchased from Dollond of London for 7.7.0 by the New Zealand Company and forwarded to their Agents in New Plymouth N.Z. by the ship "Timandra" which arrived at New Plymouth on 24th February 1842." Narrow empty case on the stem below the note would have contained a thermometer - this however is missing. Most of the wooden rim along the right hand side of this case has been broken off. The mercury tube is just visible in places where the wood has broken away at rear of case. c.1841-42. Retailed by George Dolland (59 St. Paul's Churchyard, London). Unknown manufacturer. In fair - poor condition (thermometer is missing).
See full details
Public comments
Be the first to comment on this object record.