THE DISTRICT OF SCHEMNITZ, HUNGARY. 301 



The rhyolites of the Schemnitz district frequently assume those 

 remarkably banded and ribboned structures which are so admirably 

 exhibited by the rocks of similar composition in the Ponza Islands, 

 Lipari, Ascension, &c; but, as I propose to discuss the nature and 

 origin of this remarkable structure in all these instances in a special 

 communication to this Society, I will not dwell longer on the subject 

 on the present occasion. 



With regard to the relations of the rhyolitic to the andesitic rocks, 

 there is fortunately no room for the smallest doubt, inasmuch as the 

 beautiful natural sections of the Hliniker Thai, and the fine artificial 

 exposures of the rocks along the line of railway which has recently 

 been carried across the Carpathians by the pass of Berg, furnish the 

 geologist with abundant evidence upon the subject. In studying 

 these very instructive sections, I am much indebted to the kind aid 

 of Dr. Gustav Zechentcr, of Kremnitz, who has constructed a detailed 

 geological map of the country through which the railway passes. 

 These clear sections seen in the railway-cuttings show that the rhy- 

 olites constitute great vertical intrusive masses, forced through the 

 midst of the older andesitc lavas, and that the tuffs and agglomerates 

 belonging to the former class of rocks always overlie those of the 

 latter. 



The tuffs and agglomerates, which arc not unfrequently associated 

 with the rocks of the rhyolitic class, are in many localities found to 

 yield numerous plant-remains. The rhyolitic tuffs of Heiligen Kreuz 

 and of Jastraba, south of Kremnitz, are especially famous for the 

 fine floras they have afforded. These, and some animal remains 

 found with them, enable us to fix the period of the rhyolitic out- 

 bursts as coinciding with the latter part of the Miocene epoch ; and 

 they also serve to show that the climatal conditions of the period 

 were considerably more temperate than during the great andesitic 

 eruptions, the flora being more nearly related to that existing in the 

 same area at the present day. 



We have spoken of the rhyolitic as younger than the andesitic 

 eruptions of the Schemnitz area. There is proof, indeed, that the 

 great volcano built up by the earliest and grandest ejections, which 

 supplied such prodigious volumes of lavas and agglomerates, had 

 undergone great denudation, and was, in fact, reduced almost to a 

 state of ruin before the occurrence of the second series of eruptions 

 in their midst. The former, indeed, sustain to the latter precisely 

 the same relations which in Auvergne are seen to subsist between 

 the skeleton volcanos of Mont Dore, the Cantal, and the Mezen, and 

 the more recent volcanic outbursts (forming the " puys ") which 

 have taken place in the midst of their ruins. 



Of still more recent date than the rhyolites of the Schemnitz dis- 

 trict are the sporadic outbursts of basaltic rocks, of which, for the 

 most part, there remain only the central lava masses, which filled 

 the throats of these small volcanos ("puys "). Such centres of vol- 

 canic action, now marked only by intrusive plugs of basalt, are seen 

 at many points within and around the grand old volcano of the 

 Schemnitz district. At one locality, however, namely Ostra Hora, 



t2 



