THE SUN'S SPOTS. 377 



When we consider the eone in which solar spots are most 

 commonly observed (it is only on the 8th of June and the 

 9th of December, that the spots describe straight lines on 

 the Sun's disc, which at the same time are parallel with one 

 another and the Sun's equator, and not concave or convex), 

 we are struck by the fact, that they have rarely been seen in 

 the equatorial region between 3 North and 3 South Latitude, 

 and that they do not occur at all in the polar regions. They are, 

 on the whole, most frequent in the region between 11 and 15 

 north of the equator; and generally of more common occurrence 

 in the northern hemisphere, or as Sommering maintains, 

 may be. seen there at a greater distance from the equatorial 

 regions, than in the southern hemisphere. (Outlines, 393; 

 Observations at the Cape, p. 433.) Galileo even estimated 

 the extreme limits of northern and southern heliocentric lati- 

 tude at 29. Sir John Herschel extends them to 35, as has 

 also been clone by Schwabe, (Schum. Astr. Nachr. No. 473.) 

 Laugier found some spots as high as 41 (Comptes rendus, 

 torn, xv. p. 944), and Schwabe even in 50. The spot 



d'une tres haute montagne, pourrait y observer regulierement 

 les images de la troisieme enveloppe solaire, situes, en appa- 

 rence, sur le contour de 1'astre ou nn peu en dehors ; deter- 

 miner ce qu'ils ont de permanent et de variable, noter les 



periodes de disparition et de reapparition " 



"Whatever will perceptibly diminish the brilliant intensity 

 of that portion of the terrestrial atmosphere which appears 

 to enclose and touch the circumference of the Sun, may 

 contribute to render the rose-eoloured protuberances visible. 

 We may, therefore, hope that an experienced astronomer 

 may succeed, on the summit of some high mountain, in 

 making systematic and regular observations of the clouds of 

 the third solar envelope, which appear to be situated on the 

 margin of the Sun, or a little beyond it; and thus determine 

 the permanence or variability of their character, and note 

 the epochs of their disappearance nnd re-appearance . . ." 

 (Arago, Anjiuaire pour Itt46, p. 471.) 



