Original Colaba magnetogram on 1903 October 31–November 1, adopted from the WDC for Geomagnetism at Kyoto (http://wdc.kugi.kyoto-u.ac.jp/film/index/cla_1903_normal-j.html). Each bar of baseline shows a duration of 2 hr after the record start at 10 LT (Moos 1910, p. 251). We assumed the continuity of baseline to reconstruct the magnetogram. (Courtesy of WDC for Geomagnetism at Kyoto and Colaba Observatory (current under administration of the IIG)).