Solar Structure with Observation. : 195 
extent, or farther at least below the surface than is commonly 
seen. s armed, we find that the reddish-brown masses 
within the umbra are resolved into filaments, analogous to the 
penumbral ones; like them disposed in curves, and like them 
apparently in planes, whose direction is usually approximately 
rizontal. Here also we see that these umbral filaments grow 
ealled the “crystalline” type. The impression that agencies 
like those which mould the delicate crystallizations of water 
have been here engaged, is a natural 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. Gau- 
tier, that the modifications of certain spot forms recall rather the 
effects of mineral or saline deposits than that of the action of 
whirlwinds. They may certainly be said to remind us of 
deposits, but is it by a true analogy or by a superficial resem- 
blance? If we look closer; if we increase our telescopic 
power, we find that filaments which elsewhere possess a scarcely 
sensible magnitude become here of immeasurable fineness, and 
lie, not so much at the sharp angles of a crystalline deposit, (as 
they with lower powers seem to do,) as like finely carded wool. 
We may be in doubt whether to treat these “ plumes” 
of the penumbral or umbral structures, their brightness seem- 
ing to affiliate them to the former, while, on minute examina- 
5 
around a central axis was almost tas ina sculptured 
ornament, and here again the regularity of certain crystalline 
forms is suger he “plume,” however, whatever it may 
union of heterogeneous elements, and it was found on measure- 
ment to be approximately 20” in length and 10” to 12” in 
* Seen in the lower portion of the drawing. se 
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