Historical geomagnetic field data from 1896 to 1912 as observed at Tokyo by the Central Meteorological Observatory (JMA's predecessor) are referred to as Tokyo geomagnetic data. Hourly values of Tokyo geomagnetic data are available in zip files for each year.
If the data are used for publications, presentations or other purposes, KMO/JMA (Kakioka Magnetic Observatory/Japan Meteorological Agency) should be acknowledged appropriately.
Details of Tokyo geomagnetic data are given in Toya et al. (2005), and Suganuma (2004) describes the data format.
Tokyo geomagnetic data (geomagnetic field data observed in Tokyo from 1896 to 1912) are provided here. The data interval is hourly. Data are recorded in IAGA-2002x format and stored in zip files.