1898-99. MAGNETIC INFLUENCE OF SUN ON THE EARTH AND ON COMETS. 349 
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daily mean readings of the Bifilar during the first half of 1894. You 
will not be surprised after looking at it to hear that a very great spot 
was visible from February 16th to the 28th. A slight depression may 
be seen on the 16th, when it appeared, but the full violence of the 
storm does not break out until the 22nd and 23rd, when it was central. 
Note the repetition of the depression on March 22nd, April 18th, 
May 14th, and June roth to 13th—all periodical, corresponding with the 
sun’s rotation term. The cause of the great spot was influencing the 
magnet every time its position faced the earth, long after the spot itself 
had been absorbed or filled up. 
Almost every magnetic storm, sun-spot-attended or not, repeats thus 
regularly, often to the day, for several months. It may be asked, why 
not invariably, and to the precise hour? The disturbed area on the sun 
is usually so large, as we may fairly argue from the great size of the 
spots it causes, that parts of it face the earth for more than a day, 
and the eruption which causes the storm may be in a different part 
of that area, at each successive rotation. Nor am I yet prepared to ad- 
mit that the radiation of force is in a single direct line from sun to earth. 
