Portuguese Compass Box

Arcenal do ExercitoXVIII-XIX century

Naval Museum

Naval Museum
Madrid, Spain

This case contains a range of instruments used for cartography and mathematical calculations. They include a ruling pen with spares, 2 pencil cases, a variety of spares for both reduction and clamp compasses, and a flat scale with a graduated ruler on the front for cross sections. On the back it has an equivalency scale reminiscent of a Gunter's sector, used for trigonometric and logarithmic calculations. There is also another Gunter's sector, on the front of which are string lines, solid lines, bullets, and metals (lead, silver, iron, tin, and leather) with their corresponding signs. It would have originally had a graduated semi-circle but this has not been preserved.

All these instruments allowed the navigator to make the calculations required to determine their route on the nautical chart and do topographical calculations.


  • Title: Portuguese Compass Box
  • Creator: Arcenal do Exercito
  • Date Created: XVIII-XIX century
  • Location Created: Lisbon, Portugal
  • Provenance: It bears the inscription "Arsenal Real do Exercito nº117." The Royal Arsenal of the Army was an industrial unit in the Portuguese army that manufactured and distributed different materials to both army and navy.
  • Type: Scientific Instrument
  • Original Source: Museo Naval Madrid.
  • Rights: Museo Naval, Madrid - All Rights Reserved
  • Medium: Brass and Steel
  • Length: 20,6cm
  • Height: 6,5cm
  • Depth: 9,6cm

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