312 J. W. JTTDD ON THE ANCIENT VOLCANO OF 



" massive- eruptions " than that which he supposed to have given 

 rise to the latter. 



I will now proceeed to describe in detail the conclusions to which 

 I have been conducted by a careful study of the volcanic rocks of the 

 Schemnitz district, with the aid of the light thrown upon them by 

 the labours of former investigators. 



The epoch of maximum volcanic activity in Hungary was that 

 true " age of lire " in our hemisphere, the Miocene period. So grand 

 was the scale of the outburst of igneous forces at that time, so 

 great the destructive effects on older deposits, and so enormous the 

 accumulations of ejected materials piled above them, that the task 

 of tracing the nature of the first symptoms and movements which 

 heralded the appearance, and constituted the earlier stages of this 

 tremendous manifestation of subterranean activity is a very difficult 

 one. 



The volcanic outbursts of the Miocene period were certainly pre- 

 ceded by a period of long and continuous, though irregular, upheaval 

 throughout the areas in which they took place. The marine 

 deposits of the Cretaceous and Nummulitic periods were succeeded 

 by the wide-spreading estuarine and lacustrine sediments of the 

 Oligocene, the latter formations consisting in Hungary and Transyl- 

 vania of fresh- and brackish-water strata, having a thickness of 

 several thousands of feet and containing beds of true coal, in one 

 case of a thickness of 90 feet. Now various deposits of rocks of 

 chemical origin testify to the fact that even before the close of the 

 Eocene period, the subterranean forces were beginning to exhibit at 

 the surface their most feeble manifestations, namely gaseous ema- 

 nations and hot and mineral springs. But that even at this earlier 

 stage some true volcanic fissures were formed, along which were 

 thrown up a succession of cones, the isolated " necks " of teschenite 

 and pikrite in Silesia, which have been so ably investigated by Ho- 

 henegger and Tschermak, abundantly testify. Nor is similar evidence 

 wanting in Hungary. Dr. von Hantken, the Director of the Hun- 

 garian Geological Survey, pointed out to me that in the midst of the 

 Visegrad group of mountains small deposits of tuff occur interstra- 

 tified with the coal-series of the Oligocene; and this fact is recorded 

 in the memoir which is published on this district by the Geological 

 Institute of Hungary. 



Dr. Szabo also suggested to me that some isolated masses of 

 quartz- trachyte rocks near Buda-P.esth, which are totally different in 

 composition and character from the widely spread andesitic lavas of 

 the Miocene, might not improbably belong to this earliest stage of 

 the great volcanic outbursts. It is not surprising, however, to find, 

 both in Hungary and the adjoining countries, that the subsequent 

 eruptions of the Miocene period on so grand a scale, and upon the 

 same sites, have almost entirely destroyed the evidence concerning 

 the first feeble manifestations of those forces which culminated in 

 such tremendous displays of violence. 



That the grandest of the Tertiary volcanic outbursts into Hungary 

 and Transylvania — those namely which gave rise to the formation 



