A portable mercurial artificial horizon in a leather case, manufactured by Cary of London, England, 1907.

The artificial horizon was used, especially in field observations, to establish the elevation of the sun or a star when the horizon was not visible. The vertical angle between the sun or star and its reflection in the mercury was measured; this was halved to establish the angle of elevation above the horizon.

This instrument was used by Sir Ernest Shackleton on his journey to the South Pole in 1908 (British Antarctic Nimrod Expedition) when a Farthest South record was established.

Physical Description

Rectangular, leather-lined case inside and out. Leather buckled shoulder strap, leather fastening strap and metal buckle. Text stamped into top of case. There are two partitions inside case. One partition contains a folding, hinged metal and glass triangular roof, with text printed in white on one side. The other partition contains a shallow metal tray, partly lined with green felt, with a central bath painted black. A metal container with screw top fits inside the bath cavity. The container has a crack along the bottom edge.

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