Rare Strasser & Rohde German copper-plated geodetic fiel...

Estimate

£7,000 - £10,000

Rare Strasser & Rohde German copper-plated geodetic field regulator with half-seconds pendulum and electrical contacts, No. 285, circa 1904, the 5.3" circular silvered dial of regulator format within a brass bezel and signed in the centre Strasser & Rohde Glashütte i/Sa., with outer minute ring with Arabic five minute markers, the upper subsidiary dial with markings for 24 hours with polished steel central winding square, over the half-seconds dial engraved No. 285 to the centre, finely sculpted blued steel hands,  brass movement plates with old lacquer finish, comprising a brass backboard bracket with three pillars supporting the movement backplate and pendulum, the movement with smaller front plate punch-numbered 265 at the top secured by four pillars, the reverse train with maintaining power to the barrel with indirect drive to the off-set winding assembly with lacquered brass integral pulley with steel nose to secure into the indirect wind assembly for travel purposes, the high-count going train with frosted gilt wheels with five crossings and polished steel pivots, pinions and arbors, the 'scape wheel with inverted adjustable steel pallets, indirect steel crutch-piece with fine regulation, the pendulum suspended from the brass backboard bracket with extended arm to make/break the electrical contact system, the pendulum numbered 265 to the suspension block and with weight tray to the rod, the bob signed RIEFLER MÜNCHEN D.R.P. 100870265. with fine calibration nut and steel pointer beating against a silvered beat scale calibrated 120-0-120, the case designed to safely transport the movement and pendulum intact having two securing points for the pendulum; steel pincer brass bars for the invar rod and a hinged brass bar and securing socket for the bob, oak compartments below for the weight and drawer for the original ebony-handled winding key and sub-compartment for the weight tray; the movement entirely encased within a copper-veneered cover with glazed apertures for the dial and pendulum
29½" high
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** Provenance - Christies  ex lot 1, Magnificent Clocks, 15 Sept 2004
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** From the David Read Collection

More Information

From the David Read Collection

GEODETIC FIELD CLOCKS
Geodetic field clocks were used by measuring the arc of a pendulum swing in relation to the gravitational pull of the earth and its geographical positioning, which in turn enabled a scientist to establish the exact distance to the centre of the earth, or an unknown height. This process was known as Schwerebestimmung or Gravity Fixing. In 1896 Strasser & Rohde received orders to make Geodetic Field clocks for the Royal Prussian Geodetic Institute in Potsdam, the Central European Bureau for Latitudinal Measuring, the German Navy, The Danish Army, The Imperial Russian War Ministry and the Science Museum, London. The German South polar Expedition of 1901-1903 took a half second field clock with them on their expedition.

Earlier half-second field clocks, Nos. 141, 174, 193, 194 and 238 had identical specification but were equipped with Strasser & Rohde mercury compensated pendulums costing 450DM. Records show that in January 1914 the pendulum for field clock No. 174 was exchanged for a Riefler pendulum at the cost of 600DM.

The present Strasser & Rohde No. 285 was the first half-second field clock to be delivered with its original Riefler pendulum. The pendulum was delivered to Strasser & Rohde on 21 October, 1904, then in 1905 the clock was sent to its new owner, thought to be the the Imperial Russian War Ministry