Field Traces Early Record Keeping

Although compasses had been the tool of navigation for centuries, it was not until about 1836 that Carl Friedreich Gauss (Figure 1.8), of Goettingen, Germany, investigated the global distribution of field disturbances. He organized the cooperative effort of several European magnetic observatories to try to understand why small variations in the northward magnetic direction often occurred. In those times, the research magnetometer was simply a compass with a long 1- to 2-foot magnetized needle that moved over fine angle marks to indicate the pointing direction (Figure 5.1). At prearranged times, each scientist used a magnifying lens to observe and record the angular change in the end of the northward-directed compass needle at his national observatory. The

FIGURE 5.1 ► Until the mid-nineteenth century, when photography came into general use, the measurement of geomagnetic field changes depended on the visual observation of a compass needle direction.

collaboration by Gauss and his colleagues verified that most of the observed magnetic field variations were simultaneous at all locations and therefore such fields were of natural origin and not just a local anomaly.

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