siphon barograph in wooden case
Date: late 19th-early 20th Century
Inventory Number: 1998-1-0308
Classification: Barometer
Subject:
User: Blue Hill Meteorological Observatory (1885-present)
Cultural Region:
City of Use:
Dimensions:
95.7 x 4.3 x 2.2 cm (37 11/16 x 1 11/16 x 7/8 in.)
108.6 x 8 x 8 cm (42 3/4 x 3 1/8 x 3 1/8 in.)
Accessories: packed in wooden case with cotton
Description:
Siphon barometer consisting of a glass tube bent up at the end, with the top end closed, and nearly filled with mercury. The instrument is tightly packed with cotton in a wooden case, and there is a length of string tied around the tube near the top, and at the middle. The case opens on three small metal hinges, and there is a small metal latch to close it. There is also a small metal hanging loop at the top of the case.
Signedunsigned
InscribedWritten in black paint on front of wooden case: 417 / This End / up
FunctionSiphon barometers such as this one could be used on their own to take measurements of atmospheric pressure, or, in some cases, they could be connected to a recording device via clockwork and used in a barograph.
Originally hailed as more portable than more basic mercury barometers, siphon barometers work by filling the tube with mercury through the unsealed end, while the instrument is upside-down, with the sealed end down. A partial vaccuum is created when the instrument is turned upright and the mercury flows away from the sealed end. When the merucury is balanced by the atmosphere acting on it from the open end, the height of the column corresponds to the current atmospheric pressure and can be measured.
Originally hailed as more portable than more basic mercury barometers, siphon barometers work by filling the tube with mercury through the unsealed end, while the instrument is upside-down, with the sealed end down. A partial vaccuum is created when the instrument is turned upright and the mercury flows away from the sealed end. When the merucury is balanced by the atmosphere acting on it from the open end, the height of the column corresponds to the current atmospheric pressure and can be measured.
ProvenanceIn DPW's handwriting: May 15, 1960 from the Blue Hill Meteorological Observatory.