Secular variation of magnetic declination (Gellibrand)
Variación secular de la declinación magnética (Gellibrand)
- Date
- 1634 (publicado en 1635) · confidence high
- Place
- Gresham College, London, England, United Kingdom
- Credited to
- Henry Gellibrand
- Field
- Movement
What was discovered
By comparing London measurements of 1580, 1622 and 1634, Gellibrand showed that the compass declination changes with time, contradicting the idea of a fixed deviation at each place. It meant it had to be measured again periodically.
What it led to
- dated magnetic variation tables on charts
- Halley's isogonic charts
- study of terrestrial magnetism and its origin