Variation compass
Brújula de variación y declinación magnética
- Date
- c. 1530-1580 · confidence medium
- Place
- Nuremberg and Seville (Casa de la Contratación)
- Credited to
- Georg Hartmann (declination, 1510), Robert Norman (inclination, 1581), pilots of the Casa de la Contratación
- People
- 👤 Georg Hartmann1489–1564
- Field
- Movement
What it is
An instrument that measured the deviation between magnetic and true north using an alidade and solar observation. It allowed course corrections and revealed that the Earth itself is a magnet, the subject of Gilbert's De Magnete (1600).
Columbus had already observed the variation in 1492; Hartmann measured it in Rome in 1510; the knowledge accumulated gradually.
What it led to
- Corrected oceanic navigation on the Iberian routes
- Terrestrial magnetism as a scientific problem (Gilbert, Halley)
- Attempts to determine longitude by magnetic variation
Built on
- Mariner's astrolabec. 1480-1500
- Magnetic compass
Made possible
- Magnetic dip (Hartmann and Norman)1544 (Hartmann) / 1581 (Norman)
- Secular variation of magnetic declination (Gellibrand)1634 (publicado en 1635)
- First isogonic chart (Halley's magnetic variation chart)1701
- Geologic compassc. 1954
- Halley's magnetic variation chart (1701)
- Compass with corrected rose
- Dip needle