The eclipse of 8 June 1918 was of special in terest to astronomers in the United States be cause the path of totality extended entirely across this country in a diagonal direction from Washington to Florida. The duration of total ity exceeded two minutes in Washington, but this time diminished to less than one minute in Florida, and as the sun was very low in the west when the eclipse occurred to Eastern ob servers, nearly all eclipse parties were stationed in the far Western States. Owing to world conditions, these were exclusively American. Observers from the Allegheny Observatory, the Chamberlain Observatory, the Lowell and Sproul observatories, the observatory of Drake University and others were located in Colo rado; from the Mount Wilson Solar Observa tory and from the Yerkes Observatory, the par ties were in Wyoming, while the party from the Lick Observatory (whose elaborate instru ments, employed in the eclipse of 1914, were still detained in Russia), were in Washington. The party farthest east was from the Smith sonian Astrophysical Observatory: this lo cated in Kansas in order to ensure the spread ing out of observers along the path as much as possible and so to increase the chance of avoiding bad seeing, which might be purely local. Observations were made for determin ing the rotation of the corona, while photo metric measures of its light and many photo graphs of its form were obtained, the weather being favorable almost throughout the entire path. Photographs were also secured to test the theory of relativity, but the results of this work cannot yet be given.
Bibliography.—The general theory of eclipses and the methods for their computation have been developed by Bessel in the (Astronomische Nachrichten,> Nos. 151 and 152, but with the utmost rigor in his (Astronomische Untersuch ungen' (Vol. II); a full development of Bes sel's method is given in Chauvenet's (Spherical and Practical Astronomy' (Vol. I), and in
The Theory of Eclipses) by Roberdeau Bu chanan. The most reliable general tables for the computation of eclipses are those of New comb, (Astronomical Papers of the American Ephemeris' (Vol. I). Oppolozer's 'Canon der Finsternisse,) published as Vol. LII of the ten) of the Vienna Academy con tains the elements of 8,000 solar and 5,200 lunar eclipses occurring between the dates —1207 Nov. 10 (Julian) and 2161 Nov. 17 (Gregorian), and the accompanying charts show the approxi mate path of each eclipse on the earth's surface. A valuable accessory to Oppolzer's 'Canon' is found in Dr. R. Schram's (Tafeln zur Berech nung der naheren Umstinde der Sonnen finsternisse,> published in Vol. LI of the Vienna Ginzel, in the 'Sit zungsberichte of the Vienna Academy, LXXXV, LXXXVII and LXXXIX, and in his (Spezieller Canon der Finstevnisse,' published by the Berlin Academy, has brought together a large array of references to ancient eclipses and compared them with computation. The papers of Airy, Williams, Maguire and S. J. Johnson in the Monthly Notices of the Royal Astronomical Society are of interest. The physi cal data and problems of total solar eclipses are treated in a vast modern literature mostly is sued by the observatories and learned societies. A highly important compend of physical in formation concerning total solar eclipses is that of Ranyard, (Memoirs of the Royal Astronomical Society' (Vol. XLI). For the later eclipses the most valuable discussions are to be found in the publications of the United States Naval, Harvard, Lick, Yerkes and Smithsonian observatories, in the (Astrono mische Nachrichten,) the 'Memoirs) and the (Monthly of the Royal Astronomical Society and in the Astrophysical Journal.
Revised by ERIC DooLirrLE.