quite extensive in the equatorial plane of the sun where they united in a formation like the petals of a narcissus while at the solar poles they were shorter and extended in well-defined rays. Yet no matter what its form, it is a magnificent background during the sun's eclipse for the narrow rim of deep crimson projects beyond the inky edges of the moon.
The corona seems to be caused by electrical discharges in a medium of fine dust and rarefied gases, chiefly coronium and proto-fluorine. Various electrical phenomena take place in the strong magnetic fields of the sun as a whole and in the sun-spots, and the changing fields of magnetic force cause the changing appearance of the corona.
The sun-spots, however, are of the greatest interest to amateurs for these may often be seen with very little optical aid. These dark, movable spots were first noted by Galileo, although the idea that the sun could have spots upon its surface was ridiculed by the scholars of the medieval schools who argued in the fervid language of scholastic philosophy and medieval dogmatism, that the sun was a sphere of pure fire undefiled by any spots.
Sun-spots are, as a rule, thousands of miles across and usually appear in groups which cover an immense area on the surface of the sun, but, since the sun lies 93,000,000 miles away, a spot large enough to contain the earth would appear to us about the size of a pinhead on a pincushion. Right here one should be warned again not to attempt to look at the sun without adequate protection (such as smoked glasses) for the eyes. A photograph taken through a large telescope is the most satisfactory. Although these dark blotches—which are only comparatively dark—were called "spots" and were later drawn as saucer-like depressions, modern research and increased power in the telescopes has revealed them as gigantic solar tornadoes. These tornadoes usually last from a few days to several months, and are especially numerous
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