1858.] ABICH ^ETNA. 117 



June 23, 1858. 



HandeU Cossham, Esq., Shortwood Lodge, Mangotsfield, was 

 elected a Fellow. 



The following eommunications were read : — 



1. On some Points in the History and Formation of Etna. 

 Ey Dr. H. Abich, For. Memb. G.S. 



[In a letter, dated St. Petersburg, March 3, 1858, to Sir C. Lyell, F.G.S., &c.] 



Your questions about Etna have carried me back to the pleasant 

 time when I made repeated studies of that remarkable mountain, 

 not having a presentiment of the occasion which I much later had 

 of verifying and recognizing in another land the truth of those 

 beautiful laws of nature, written so clearly in the configuration of 

 the Yal di Bove, and especially in the structure of the very body of 

 Etna, visible on the slopes and steep declivities of that enormous 

 chasm of subsidence, the Yal di Bove. For, that it is indeed such, 

 nobody will deny who has been enabled, by comparative researches 

 in the whole circumference of the elliptical valley, to prove that 

 idea of its formation, — an idea indeed which immediately suggests 

 itself to the observer from the elevated edge of the Val di Bove on 

 the border of the Piano del Lago or Schiena dell'Asino. 



You are struck by some particulars in my figure of the mountain 

 in PI. 8 of my ^ Yiews of Etna*,' and you desire to know how far 

 those lines pointed out in your copy of it are based upon direct 

 observation ? In general, I have to confess that, when tracing those 

 dotted lines, I may have forgotten that it was not the right place, 

 in a profile constructed by hypsometrical measurements only, to hint 

 at theoretical views, and that it would have been better to suppress 

 not only the dotted line, but also those lines indicating a stratifica- 

 tion, and intended to express a general law of structure applicable 

 to the whole. 



First, vdth regard to the lines of stratification. When opening 

 my journal of those excursions on Etna, I have many proofs of my 

 having seriously sought for a constancy in the dip of the planes of 

 stratification in the central region of the mountain ; but I found none. 

 Such indications as appeared to be visible on the side of the Serra del 

 Solfizio and the Hocca Giannicola seem to have only a local signifi- 

 cation. At times I found the dip to be away from the valley ; and 

 at other places the dip was towards it. Independently of these 

 anomalies, I could not but lay considerable importance on the general 

 tendency amongst the upper beds in the central region of the Serra 

 del Solfizio to horizontal stratification (fig. 4 a, a\ 6), with an appa- 

 rent sHght dip towards the vaUey on one side, and the contrary on 

 the other (fig. 6). I observed, too, that the dip in the Cistema 



* Erlauternde Abbildungen geologischen Erscheiaungen beobachtet am Vesuv 

 und Aetna in den Jahren 1833 und 1834, von Dr. H. Abich. 1837. 



