THE DISTRICT OF SCHE1INITZ, HUNGARY. 311 



suggestions as to the form and structure of the great volcano of 

 which they constitute the ruins. He showed* that the mining- 

 district of Schemnitz, a comparatively low-lying tract of oval 

 form, about 20 miles long by 15 broad, was surrounded and over- 

 looked on all sides by steeply scarped mountain-masses, rising to 

 heights of from 3000 to 4000 feet above the sea. This encircling 

 wall, as he pointed out, consists of great masses of andesitic lava, all 

 exhibiting a slight dip away from the central depressed area, and 

 alternating with enormous accumulations of tuffs aud agglomerates, 

 the whole being not unfrequently traversed by mineral veins ; while 

 in the central area rise numerous masses of rhyolitic and basaltic 

 lavas and tuffs. Here, as the able Hungarian geologist clearly per- 

 ceived, we have presented to us tho characteristic features of a great 

 volcanic cone, with a central crater of enormous dimensions ; and 

 he not inappropriately compared the Schemnitz crater with its 

 central masses of acid rocks and its walls of more basic materials, 

 to the well-known crater of liocca ITonfina with its enclosed bosses 

 of rocks, forming the mountains of Santa Croce. 



At the time when Yon Pettko wrote (1848), the "elevation- 

 crater" theory of Von Buch was almost universally accepted by 

 foreign geologists, and the example of Rocca 3Ionfina was regarded, 

 on the authority of Abich, as affording a most signal illustration of 

 its truth. It is not surprising, therefore, that Yon Pettko should 

 have adopted this view of the origin of the great crater of Schemnitz, 

 and declared it to be a magnificent example of an " elevation- 

 crater." The facts and arguments adduced in support of this once 

 famous theory by Yon Buch, Humboldt, and Elie de Beaumont have 

 been so utterly demolished by the observations and reasonings of 

 Lyell, Scrope, and Constant Prevost, that it would be mere waste of 

 time at the present date to treat the theory as one still possessed of 

 any vitality. But as regards all the other conclusions of Yon Pettko 

 concerning the Schemnitz district, I believe that they have been 

 fully substantiated by further observation. 



Bichthofen, who, at a somewhat later date, made a general study 

 of the Hungarian volcanic rocks, arrived at some interesting conclu- 

 sions as to their relations. He correctly defined their true sequence 

 of eruption to have been as follows — first the trachytes, secondly 

 the rhyolites, and thirdly tho basalts ; but, probably from failing to 

 perceive and take account of the enormous amount of denudation 

 which these volcanic masses had been subjected to, he was led to 

 conclude that only the latter two classes of rocks could be regarded 

 as having had a true volcanic origin. The vast masses of trachytic 

 lavas with their tuffs he referred to a series of " massive-eruptions ; " 

 and not recognizing the essential identity in the chemical and mine- 

 ralogical constitution between the " greenstone trachytes " and the 

 ordinary trachytes of the district, he applied to the former the name 

 of " propylites," and assigned their origin to an older series of 



* " Erhebungskrater in der TJingebnng von Schemnitz nnd Kreramtz," Be- 

 richte iiber die ^littheilungen von Freunden der Naturwissenschaften in Wien, 

 Bd. iii. p. 199. 



