Artificial horizon, made by Troughton & Simms, London. Used at both Williamstown Observatory and Melbourne Observatory, and for Geodetic Survey of Victoria.

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.

Physical Description

Rectangular metal trough covered by metal roof with two inclined panes of clear glass to prevent wind from agitating the surface of the mercury. Mercury contained in metal container with conical lid. In cedar case.

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