It was long ago discovered that if one starts northward from the magnetic equator, the compass-needle soon begins to dip downward (and northward). At the southern border of the United States, the downward inclination amounts to about 57 degrees. At the borders of North Dakota and Maine the dip is about 76 degrees. By the time Hudson Bay is reached the needle assumes a vertical position. This means that it is here suspended immediately over the north magnetic pole itself. At the magnetic equator in Peru, a needle suspended by a thread is exactly balanced. Dr. See states that at the North and South Poles there is a downward pull—by the magnetic force—of just one millionth of the gravitational force, while in Peru the total magnetic force is precisely one ten millionths of gravitation. It has been found that both the North and the South Poles are anything but fixed in position. They “wander about in their subterranean region”. In the course of centuries, the compass-needle swings from west of north, and then to the east. Even the amount of the dip slowly changes, in a periodic way, and at every point on the earth. For example, in 1576, the north end of the needle at London dipped at an angle of 71 degrees 50 minutes. By 1720 the angle had increased to 74 degrees 42 minutes—almost up and down. Since then, the dip at London has continually decreased. At the present time we are puzzled by the fact that the inclination of the dip is 66½ degrees at London and more than 70 degrees at Washington. It has long been known that variations in magnetic declination of the delicately mounted needles, in observatories, are directly correlated with solar disturbances. The late Dr. A. Wolfer (sometime director of the Zurich Observatory) was the first to show us how closely the curve of the sun-spot activity rises and falls with the fluctuations of magnetic declinations. Before attempting to explain the peculiarities of magnetic action in terms of the modern electromagnetic theory, it will be well to recall certain stages of progress in the development of this theory. This plan will permit elucidation of the theory itself by “easy steps”. FOOTNOTES: [3] Cf. Whittaker, E. T., “A History of the Theories of the Ether and Electricity from the Age of Descartes to the Close of the Nineteenth Century,” Dublin and London, 1910. See also, Comstock and Troland, “The Nature of Matter and Electricity,” New York, 1917; Steinmetz, Dr. Charles P., “Elementary Lectures on Electric Discharges, Waves and Impulses and Other Transients,” New York, 1914; and Starling, Dr. Sydney G., “Electricity,” London and New York, 1922.