1887 20 May 499/1 The earthquake was recorded automatically upon the magnetographic traces in the observatory.
1939 93 70 The magnetographic records of declination, horizontal force, and vertical force at the Dehra Dun Observatory.
1976 15 Jan. 87/2 This slow run of the signal was eliminated (especially when we compared the records of two independent magnetographs in our double-channel magnetographic system).