4 MEMORIE DELLA SOCIETÀ' 



fications of certain spot forms recali rather the effects of minerai or saline depo- 

 sits, than tliat of the action of whirlwinds. They may certainly be said to re- 

 mind us of sudi deposits but is it by a true analogy, or by a superficial resem- 

 blance? If we look closer; — if we increase our telescopio power; — we flnd that 

 tilaments which elsewhere possess a scarcely sensible magnitude, become here of 

 imnieasnrable fineness, and lie, not so much at the sharp angles of a cristalline 

 deposit, (as they with lower powers seem to do), as like fìnely carded wool. We inay 

 be> in doubt whether to treat these « plumes » as part of the pemimbral or uin- 

 bral strncture, their brightness seeming to affiliate them to the former, while on 

 minute examiuation, their fibres may yet be discerued prolonged through the am- 

 bral shade and rising again (apparently) above it, in the luminous points just re- 

 ferred to. The resemblance seen here then is rather to the filamentary types found 

 in the chromospherc, and which no oue qnestions are purely gaseous. There is fre- 

 quently remarkable symmetry displayed in these forms, but very rarely as much 

 as in the present example , which was the inost regalar I have ever seen, The 

 balance of its parts around a centrai axis, was almost as exact as in a sculptnred 

 ornamcnt, aud here again the regularity of certain crystalline forms is suggested. 

 The « piume » however whatever it may be, is evidently an integrai strncture not 

 due to the casual union of heterogeueous elements, and was found on measure- 

 ment to bc (approximately) 20" in length and 10" to 12" in width. Are we prepa- 

 red to admit the existence of a body properly analagons to a « crystal » covering 

 over ten tiuies the area of Europe? Even on the Sun where everything is euor- 

 mous this taxes belies. But once more, the extremely attenuated filaments of the 

 « piume » do uot appear to lie in any single piane. The great length of nearly 

 10000 Euglish miles, throngh which they apparently extend, is a curtate distance, 

 or that in which we see them as projected on the appareut piane of the solar 

 disc. If I do uot misiuterpret the iudications given by the brightening ends , 

 they can hardly lie spread npon the surface of a liquid, or upon any single sur- 

 face whatever, — they bend down aud up. AH throngh the umbra are to be no- 

 ted similar appearances; we seem to look down through increasing depths, but as 

 far as vision extends, without coming to any liquid or solid fìoor — always down 

 through volumes of whirliug vapor (« whirling » if we judge from their forms, which 

 are disposed as if by vortical action) , and grow fainter till lost to sight at an 

 unknowu dcpth below the surface. Speaking then without reference to any hy- 

 pothesis it seems to me that the resemblance to crystalline structure though I 

 agrec that it is strikiug, does not appear to be more tban superficial. We have 

 at certain rare intervals remarkable cirrous clouds in our own atmosphere, whose 

 resemblance to these forms is equally dose , and in which I think we may see 

 not only a resemblance but an analogy. Some of these rarer cirrous types of our 

 own sky, which I have stndied in connection with solar forms, might so far as 

 external appearauce went , certainly be fancied to display crystalline action as 



