ANNIVERSARY ADDRESS OF THE TRESIDENT. xllii 



aminations have not yet reached the two greatest of these features — 

 the range extending north and south from Eperies to Tokay (which 

 cuts off the whole mass of the crystaUine and older sedimentary 

 rocks of the southern half of the Carpathians on the east, like a grand 

 fault of dislocation, and yet does not cause any disturbance in the 

 regular course of the sandstones lying on the north), and then, 

 secondly, the still more extensive range from Vihorlat to Gutin 

 (stretching from north-west to south-east, and which is probably 

 continued in the Hargitta of Transylvania). But our labours already 

 include the thick and more boss-shaped masses of the Matra group, 

 of the Ore Mountains of Schemnitz and Kremnitz, and, lastly, of the 

 neighbourhood of Gran. Especially do the Trachytes appear in the 

 latter district abundantly, in contact with newer fossiliferous Tertiary 

 rocks. It is evident that an older portion of these, which probably 

 belongs to the horizon of the Upper Oligocene formation, contains no 

 trace of the debris of the trachytic rocks — that these last, on the 

 other hand, occur frequently in great abundance in the Leitha 

 limestone and the marine Miocene beds of the age of the deposits of 

 the Vienna basin (a proof that the trachytic eruptions of this country 

 at least had their origin in the beginning of the Miocene period). 

 The close of this period of trachytic eruptions occurs at the time of 

 the deposition of the Cerithium-beds. 



*' The work accomplished by Richthofen, at the time of the first 

 general outline of our survey, with such excellent results, relating to 

 the discrimination and separation of the different branches of the 

 trachyte family, which in great part differ from one another in an- 

 tiquity, has been since much enlarged and completed, especially 

 by Dr. G. Stache. To the groups of the EhyoKtes, first proposed 

 by Eichthofen, including the true trachytes and the greenstone-tra- 

 chytes, Stache has added a further series in the older quartzitic 

 trachytes or ' Dacites.' 



" Very interesting results have been obtained by Carl von Hauer 

 and other chemists through their valuable analyses, not only of the 

 rocks in general, but also of the felspars crystallized out in them. 

 The analyses show that in the Hungarian and Transylvanian rocks 

 of the trachyte family, in what relates to the degree of acidification, 

 all the members of the series hitherto known, from the most basic to 

 the most acidic, are represented. In the nature of their felspars, on 

 the other hand, these rocks differ materially from the rocks of all 

 trachytic districts that have hitherto been carefully examined ; they 

 are in fact chiefly basic lime-soda-felspar, wavering between La- 

 bradorite and Oligoklase, probably corresponding to what has been 

 called by Abich and others "Andesine." This lime-soda-felspar forms 

 the principal ingredient of the basic Andesite and Greenstone tra- 

 chytes ; in the more acidic Dacite, Sanidine appears with it ; in the 

 still more acidic Rhyolite, finally, the whole of the felspar appears to 

 consist of nothing else but Sanidine. 



"And, though it does not concern the area of our Austrian survey, 

 I would here also allude to the analyses (carried on in our laboratory) 

 of the volcanic rocks brought to the surface by the latest eruption 



d2 



