296 J.. W. JUDB ON THE ANCIENT VOLCANO OF 



" quartz-porphyrites." The " dacites," or quartz -andesites, are 

 not of frequent occurrence in the Schemnitz district, but are seen 

 at a few points, as the Hodritsch Thai near Schemnitz, the Kopa- 

 nitzer Thai near Dilln, and the Berg Szitnya near Sz. Antal ; but 

 in some other parts of Hungary and throughout Transylvania they 

 have a very wide distribution. 



The agglomerates, tuffs, and ash-beds which are associated and 

 alternate with the sheets of lava are almost wholly made up of 

 fragments of volcanic rock, sometimes mingled with portions of the 

 subjacent sedimentaiy deposits. In some places the agglomerates 

 consist of irregular masses of all dimensions, including blocks of 

 prodigious size and weight, confusedly heaped together ; at others 

 they pass into the most perfectly stratified tuffs and ashes. Such 

 stratification in the ejected volcanic lapilli and sand must not, how- 

 ever, in the absence of marine or freshwater organic remains, be ac- 

 cepted as any proof of their having been accumulated beneath water; 

 for, as we know from the example of many recent volcanos, ejected 

 materials in falling through the air, or while being swept down the 

 mountain-slopes in those torrents of mud so characteristic of great 

 volcanic outbursts, may assume the most perfectly stratified and even 

 finely laminated condition. The masses of volcanic agglomerate, as 

 well as the rocks on which they rest, are frequently seen to be 

 traversed by numerous dykes of lava. 



The more finely divided tuffs and ashes are not unfrcquently 

 found to contain numerous remains of plants. These have been 

 most carefully studied, and their relations to the existing flora and 

 to those of earlier geological periods very clearly determined by 

 Ungcr, Yon Ettingshausen, Kovats, Andrae, Heer, and Stur. Erom 

 the examination of these plant-remains wo are enabled to infer the 

 conditions of climate, soil, and elevation which distinguished the old 

 land on which these volcanic eruptions took place. Besides the 

 plants, some remains of terrestrial mollusca, reptiles, and mammals 

 have also been found imbedded in these volcanic tuffs. 



That these agglomerates, tuffs, and ashes were formed by 

 the ordinary explosive volcanic action, there is, I think, not the 

 smallest room to doubt ; and that the volcano which they helped 

 to build up was a subaerial one, there is also abundant, proof. 

 That, as is so common among volcanic cones, numerous ponds, 

 marshes, and even lakes of considerable size, were successively 

 formed and filled up by the ejected materials and sediments derived 

 from them, is also, I believe, rendered sufficiently clear from the 

 lacustrine deposits with remains of freshwater mollusca and fishes 

 which are so frequently found alternating with the agglomerates and 

 lavas. But it is also evident that the ancient volcanos of Hungary, 

 like so many existing ones, rose directly from the margin of tbe 

 ocean, or rather of a more or less isolated inland sea, with semi- 

 marine or brackisb- water conditions. That into some of the de- 

 pressions among the great volcanic masses of Schemnitz the sea 

 must, from time to time, have had access, is proved by the marine 

 or brackish -water shells found in the basins of Handlova and llybnik, 



