THE DISTRICT OF SCHEMNITZ, HUNGARY. 323 



mountains (the centre of volcanic activity sometimes showing clear 

 evidence of having shifted along a line of fissure), which has been 

 formed by enormous and frequently repeated eruptions of andesitic 

 lavas and tuffs. In every instance we find proofs that the more 

 deeply seated masses of andesitic lava have, in consolidating, assumed 

 a highly porphyritic or granitiform structure, and that the action 

 upon these of acid gases and vapours has resulted in the decomposi- 

 tion of the mass, with the diffusion of valuable metallic ores 

 throughout the substance of the rock and their accumulation in 

 considerable quantities wherever a suitable fissure occurred in it. 

 In each of these volcanos, too, the eruption of the andesitic lavas 

 appears to have been followed, after an interval of subsidence, by the 

 extrusion of highly siliceous rocks (rhyolites) and, finally, of extremely 

 basic ones (basalt and augitc-andesite) on a much more restricted 

 scale than in the case of the older ejections. The fossil remains 

 associated with the masses of tuffs at the several volcanic centres 

 show that the ejection of the different classes of lavas took place 

 at periods which were approximately contemporaneous in each case ; 

 and at every point the decline of volcanic activity was marked by 

 the appearance of hot and mineral springs and fumaroles. 



Conclusion. 



The more important results to which we have been led by the 

 facts and arguments of the foregoing memoir may be briefly 

 summed up as follows : — 



(1) The igneous masses which in Hungary and Transylvania have 

 been poured forth at the surface, in the form of andesite and quartz- 

 andesite lavas, have, where undergoing consolidation at some depth 

 from the surface, assumed a most perfectly granitic character 

 (" syenite " and " granite " of most authors, or, more properly 

 perhaps, diorite and quartz-diorite). There is the most complete and 

 insensible transition from these granitic rocks to the true lavas ; and 

 the whole of them are of Miocene date. 



(2) Around each of the intrusive masses which constitute the 

 links between the volcanic rocks poured forth at the surface and the 

 subterranean reservoirs from which they have been derived, various 

 chemical actions have been set up in the masses of Triassic sediments 

 through which these have been extruded ; and these actions have 

 resulted in the production of highly crystalline and foliated rocks 

 which are identical in penological character with materials con- 

 stituting widely spread metamorphic areas. 



(3) But, while there appears to be at first sight a gradual passage 

 from the stratified rocks through these metamorphic masses into the 

 truly granitic rocks, yet the phenomena displayed by this district 

 really afford no support whatever to the theory that the granitic 

 masses are not truly intrusive at all, but represent sediments which 

 have undergone their final and most extreme metamorphism in situ. 

 On the contrary, not only is the chemical and mineralogical consti- 

 tution of the granitic masses far too uniform throughout and too 



