CHAP. VIII.] 



SPOTS AND FACUL.E. 



95 



Changes are going on incessantly in the region of the -spots. 

 Sometimes these are noticed after the lapse of an hour even ; a 

 portion of the penumbra setting sail across the umbra; or a 

 portion of the umbra melting from sight ; or we may have an 

 evident change of position and direction in masses which retain 

 their form. In some spots evidences of cyclonic action are 

 very obvious. 



We not only get this darkness localised in spots, but it is 

 easy to see that there is a general defect of illumination as we 

 approach the sun's edge. 



FIG. 35. Sun spot (Secchi). 



We may now pass to the brighter portions of the general 

 surface. These are most obvious near the edge of the solar 

 disc, and especially about spots approaching the edge ; in 

 these positions bright streaks of diversified form, quite dis- 

 tinct in outline, and either entirely separate or uniting in 

 various ways into ridges and network, are seen. These, 

 which have been termed faculce, are the most brilliant 

 parts of the sun. Where near the edge the spots become 

 invisible, undulated shining ridges still indicate their place, 



