No. h. m. h. m. m. s.
1.At1 30Greenwich M. T.=7 27.Local M. T. the duration is 1 12.6
2.”1 35” ” =7 47.” ” ” ” ” 1 19.6
3.”1 40” ” =8 05.” ” ” ” ” 1 26.0
4.”1 45” ” =8 22.” ” ” ” ” 1 31.7
5.”1 50” ” =8 40.” ” ” ” ” 1 37.0
6.”1 55” ” =8 54.” ” ” ” ” 1 41.9

Chart III.—Fifteen Pictures of the Solar Corona, arranged in the Eleven Year Period, to show the Recurrence of Similar Types during this Period.

An observer at the intersection of these cross-lines with the central line will see the totality during the intervals given in the table.

The mode of the formation of the shadow cones of the moon, called the penumbra for the partial shadow and the umbra for the total shadow, are well illustrated in general works on astronomy, and good geometrical pictures of them can there be found, together with much useful information regarding the subject of eclipses. As we are here concerned chiefly with certain practical points about the eclipse of 1900, it will be well for the reader to consult such works for many details regarding the astronomical features attending an eclipse of the sun which must now be omitted.

There are many existing theories to account for the phenomenon of the sun’s bright appendage, called the corona, which is visible only during eclipses, on account of the absorbing effects of the earth’s atmosphere on its light. Is it electrical, or is it magnetic? Is it composed of fine stuff ejected from the sun, or of meteoric dust falling upon the sun? Is it merely an optical effect, as some suppose, or is it a portion of the newly discovered radiant matter streaming off to enormous distances into space? The answer to these questions is eagerly sought through observation, photography, and every other possible means, on the occasion of each total eclipse.

The efforts of astronomers have thus far secured a series of pictures of the solar corona, which, when compared together, show very distinctly that the corona, as well as the spots, the protuberances, and the faculæ, are going through a series of changes which seem to repeat themselves in the so-called eleven-year period. It has also been proven, with entire distinctness, that the earth’s magnetic field, as marked by the changes in the intensity of the magnetic elements, in the auroral displays, and the earth electric currents show variations which synchronize closely with those observed on the sun; also that the weather elements of pressure, temperature, precipitation, and storm intensity all harmonize with the solar and the earth’s magnetism in the same synchronism. All attempts of scientists to detect any variations in the sunshine which falls upon the tropics have been entirely futile; on the other hand, it has been shown that the magnetic forces having the characteristics just mentioned impinge upon the earth in a direction perpendicular to the plane of the earth’s orbit, just as if the sun, being a magnet, throws out a field of force to the surface of the earth, which, by its variation depending upon the internal workings of the sun, produces the changes just enumerated in the earth’s atmosphere and in its magnetic field, also throughout the planetary system, being, of course, strongest near the sun. The belief is gradually growing among scientists that the earth, the sun, and the planets are all magnetic bodies, and have these bonds of connection between them in addition to the Newtonian gravitation. This is a most fascinating field of research, and, though full of difficulties, yet attracts the attention of many who are convinced that one of the most pressing duties of the hour is to clear up the problems connected with the transmission of energy from the sun to the earth in other forms than the ordinary or sunlight radiation. It is entirely probable that the secular variations of the weather changes from year to year, and even from month to month, are bound up with these solar forces, and that the solution of these questions will carry with them much information of practical use to civilized man.

The coronas of the past forty years are shown on [Chart III], taken from the report of the eclipse of 1896 (August 9th), by A. Hansky. It arranges the coronas in the eleven-year period so far as the dates at which the eclipses occurred permit this to be done, and by comparing them in vertical lines the similarity is at once seen for the respective quarters of phases of the period. The forecast there given for 1900 is seen to resemble 1867, 1878, and 1889, but it differs in orientation from that on [Chart IV], which was prepared by the author. The four coronas on the left in [Chart III] are taken at the sun-spot maximum, and the appearance is that of total confusion in the structure of the rays; the second and the fourth columns are for the sun’s medium intensity at about halfway between the maximum and the minimum, and they show a system of polar rays taking on structural form, the second column being at a stage of diminishing and the fourth at one of increasing solar activity; the third column gives the corona when the spots are at a minimum of frequency and the sun is in a comparatively quiescent state, wherein the polar rifts are very distinct and the equatorial wings or extensions greatly developed.