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This type of magnetometer was used by the U.S. Coast and Geodetic Survey for magnetic field observations in the early part of the 20th century. The instrument is shown in its original travelling case along with most of its accessories. The tube in the lid of the case contains the bar required for horizontal intensity measurements.
It is not known how this instrument came into the possession of the Geomagnetic Laboratory. Reports of the early magnetic surveys carried out by the Dominion Observatory make no mention of it.