Geomagnetic observations from 1600-1850

Complete text of publication follows. Direct observations of the Earth's magnetic field play a crucial role in allowing us to reconstruct the field's evolution over time. Over the last decade, we have analysed ship's logs housed in the British library, and other similar libraries in Paris, Amsterdam, Copenhagen and Madrid, which record the journeys of ancient mariners on their journeys of trade, discovery and buccaneering and on naval duties from the 16th century onwards. These archives show how the magnetic field has changed over hundreds of years; from these historical records it is possible to reconstruct the changing morphology of the magnetic field and patterns of flow of molten iron deep in the core of the Earth, giving us a unique window on the behaviour of the Earth's liquid core.