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Dip Circle

The Dip Circle is a device used to measure the angle between the horizon and the Earth’s magnetic field.
The phenomenon of magnetic dip is important in the fields of surveying, mining and aviation. The unit pictured is recorded in the National Inventory of Historic Scientific Instruments by Charles Mollan, entry 1932 UCP 159. It was manufactured by T. Blunt Cornhill, London, sometime in the 19th Century. The device comprises brass circles housed in a slim cylinder with glass on both sides. Two diagonal bars support the white metal needle. Its axis has a cross with four counter-weight screws. Below the circle housing is a right-angled brass bar which has eight line marks to denote the compass points. The housing can be revolved to any point around this.
