Dip circle

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A dip circle is an instrument for finding the vertical component of the earth's magnetic field. This example was made around 1810, probably by John Miller and Alexander Adie, scientific instrument makers based in Edinburgh between 1804 and 1822.

The brass dip circle is mounted on a brass pillar on a wooden circular base with three levelling screws. The circle is graduated in degrees, marked every 10 degrees into four 90 degree portions. The scale is signed on the back 'Miller & Adie Edinburgh'.

The dip circle was devised around 1576 by Robert Norman of London. He noticed that a carefully balanced compass needle did not stay horizontal; its inclination or 'dip' shows that the direction of the Earth's magnetic field is not parallel to its surface.

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• Online ID: 000-100-102-662-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1902.29.2
• Date: Around 1810
  c. 1810
  
• Material:
• Dimensions:
• What:
• Subject: 5. CARTOGRAPHY, Surveying (Departmental Classification)
  22. PHYSICS, Magnetism and Electricity (Departmental Classification)
  
• Who: Miller and Adie, Edinburgh (Maker)
  
• Where: Scotland, Midlothian, Edinburgh
  
• Event:
• Description: Dip circle, probably by John Miller and Alexander Adie, Edinburgh, c. 1810
  
• References:
  • For Miller & Adie, see Clarke, T.N., Morrison-Low, A.D. & Simpson, A.D.C., Brass & glass scientific instrument making workshops in Scotland as illustrated by instruments from the Arthur Frank Collection at the Royal Museum of Scotland. Edinburgh: NMS, 198 
  • McConnell, Anita, Geomagnetic Instruments before 1900: An illustrated account of their construction and use. London: 1980 
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