Magnetic Observations of Sunspots, 1917–1924

Abstract

IN these two volumes the late Dr. G. E. Hale and his colleague Dr. S. B. Nicholson give a connected account of the instrumental developments, and the observations, that proved the existence of strong local magnetic fields at the sun's surface. This account occupies fifty-seven pages of volume I. The remaining thirty-four pages contain tables giving the daily classification of every sunspot group observed at Mount Wilson from January 1, 1917, to January 1, 1925, and the maximum magnetic field-strength observed in each group. The second volume reproduces the Mount Wilson daily sketches of the sun's surface, showing the sunspot groups with their various members, and indicating the polarity and the approximate magnetic field-strength of these members. An examination of these sketches cannot but impress the reader with the wealth of results on sunspot magnetic fields that Hale and his fellow-workers have accumulated; they form a rich mine for theorists in solar physics, whose task in this field is, as yet, scarcely begun. Magnetic Observations of Sunspots, 1917–1924 By George E. Hale Seth B. Nicholson. Part 1. Pp. iii + 91 + 8 plates. Part 2. Pp. ii + 692. (Papers of the Mount Wilson Observatory, Vol. 5, Parts 1 and 2.) (Washington, D.C.: Carnegie Institution (Publication No. 498), 1938.) 10 dollars.