A brief history of geomagnetism and a catalog of the collections of the National Museum of American History

magnetism (also known as terrestrial magnetism) is the scientific study of the earth from the point of view of its magnetic properties. The alignment of a natural or artificial magnet in a north-south direction is only the best known of these. T h e discovery of other properties, such as the separation of the magnetic poles from the geographic poles of the earth and the "dip " of the needle in arctic (and antarctic) latitudes, interested the scientifically inclined as early as Columbus. Mariners, who had reason to be most interested in the compass, were prominent in the study into the 18th century. But as more and more magnetic peculiarities were discovered—the apparent movement of the poles, the changes in direction, dip, and magnetic strength from year to year and even from day to day, and magnetic irregularities apparently connected with other atmospheric phenomena—the aurora borealis—the subject was taken over by the scientists. While Alexander von Hum-boldt, famous as a scientific traveler in the early 19th century, promoted world-wide measurement of geomagnetic phenomena, less adventurous scientists occupied them-selves with the development of more sensitive instruments and more sophisticate