Bemmelen, Willem Van (1868-1941)

Dutch geophysicist and meteorologist Willem van Bemmelen was born on August 26, 1868 in Groningen (the Netherlands) as the son of Prof. Dr. Jacob Maarten van Bemmelen and Maria Boeke. As a student of physics and mathematics in his early twenties, he became interested in the Earth's magnetic field through the work of Christopher Hansteen (q.v.) (Hansteen, 1819), who had derived isogonic charts and a geomagnetic hypothesis from historical magnetic measurements gathered from ship's logbooks. Aware of Hansteen's limited coverage of the seventeenth century and the period before 1600 and having encountered an abundance of original manuscript sources in various Dutch archives during an attempt to construct a secular variation curve for the city of Utrecht, Van Bemmelen decided to fill the gap with all useful data he could find from the period 1540-1690. The results he initially laid down in his Ph.D. thesis (Bemmelen, 1893), which tabulated the original declination