DEGLI SPETTR0SC0PIST1 ITALIANI 3 



nunibral edge, elsewhere partly described, bear witness to the existence of a force, 

 or perhaps I shonld say the component of a force, directed in a general sense to 

 the centre of the spot; while at the sanie timo the absence of a common direction 

 of rotation, and the existence even of distinctly marked opposite flexnres in the 

 same filaments, show the complexity of the action which has becn at work. (C). 



2. An appearance which deserves remark is this. It has long silice been obser- 

 ved that the interior border of the pennmbra is commonly brighter than its exte- 

 rior, but the hitherto nnrecognized cause is bere shown, in a general tendency of 

 these singular obiects, the filaments, to grow progressi vely brighter toward their 

 extreniities. It should be noticed that it is not only bere meant that these grow 

 brighter at the inner edge of the pennmbra, but that the inany filaments not long 

 enough to reach wholly across the penumbra , and whose ends in this case lie 

 partly down its slope in every case show the same tendency, so that it is diffi- 

 cult to resist the impression that these extremities have a general disposition to 

 turn upward and to appear as though lifting their points above some obscuring 

 medium. (D). 



3. In this connection we may best stndy the nmbral forms previously referred 

 to, about which so little is hitherto known, owing to the darkness in which they 

 are involved, That this darkness is only relative has been long surmised, and I 

 have found by direct experi ment that wheu ali extraueous light is excluded, except 

 that troni the « blakest • part of the umbra, this proved to be not only iutrìnsi- 

 cally bright, but insnpportably intenso to the naked eye. By the optical devices 

 referred to them, I have been able to look within the Sun to some limited extent 

 or farther at least below the snrface than is commonly seen. Thus arnaed, we find 

 that the reddish-brown masses within the umbra, are resolved into filaments, ana- 

 lagous to the penumbral ones; like them disposed in curves, aud like them appa- 

 rently in planes, whose direction is nsually approximately horizontal. Here also we 

 see that these nmbral filaments , grow brighter toward their extremities, which 

 appear as if curling upward, their ends thus occasionally furnishing that appea- 

 rance of isolated bright points in the umbra which has been abready observed. 

 Leaving these for the moment let us consider what was on the whole the most 

 remarkable feature of the spot; a plumc-like appearance in its lower portion (1), 

 which in connection with adjacent peculiar curves presented forms of what I 

 have called the « crystalline » type (E). The impression that agencies like those 

 which mould the delicate crystalizations of water have been here engaged, is a 

 naturai one , and has been expressed before , the term « Photospheric Crystal > 

 having apparently been used by M. Chacornac as long ago as 1853. This part of 

 the spot, if any, would seem to justify the remark of M. Gantier that the modi- 



(1) Seen in the lower portion of the drawing. 



