14 GEOLOGICAL MEMOIES. 



paper to the Academy of Sciences of Brussels, has comraunlcated a 

 note to the Geological Society of Erance*, in which he discusses the 

 question whether the fossiliferous deposit discovered by them be not 

 comparable with the "Colonies" of M. Barrande. He concludes 

 that their discovery adds a new system to the Eocene deposits 

 hitherto known in Belgium, namely the " Calcaire grossier of Mons," 

 which underlies all the others, and which may be considered the 

 precursor of the Calcaire grossier of the Paris basin in a district 

 where that formation is not represented. He also remarks that the 

 existence of this small Eocene basin of " Calcaire grossier of Mons," 

 following the small basin of tufaceous chalk of Ciply, is a new indi- 

 cation in favour of the" formation of calcareous deposits by causes 

 which are perpetuated or reproduced in the same localities. [A. S.] 



On the Envieons of Tokay, Htjngaey. By Professor J. Szabo. 



[Proceed. Imp. Geol. Instit. Vienna, September 1865.] 



The whole of these environs belong to the Tertiary period. The 

 eruptive rocks are trachyte and rhyolite ; those of sedimentary origin 

 are the results of decomposed or disaggregated rhyolite ; and last in 

 the series comes the soil producing the well-known wines. The 

 ascending order of the trachytes, as to their geological age, is : — 

 Andesitic trachyte (Baron Richthofen's " grey trachyte ") ; amphi- 

 bolic trachyte (v. Hauer's and Dr. Stache's "genuine" or "red 

 trachyte"), less extended than the first variety, but forming important 

 and lofty mountain-groups in the south portion of the chain between 

 Eperies and Tokay; Beudant's "Trachyte micace amphibolique," 

 the extreme link of the amphibolic trachyte near Yissegrad, is want- 

 ing in the Kegjallia or viniferous hill-range of Tokay. The rhyolites 

 differ from the trachytes proper by the crystallized quartz of primary 

 formation, and by the nature of the felspars entering into their com- 

 position, which contain a large proportion of silica combined with 

 lime and soda. Sanidine is but of subordinate occurrence. The 

 rhyolites e^ddently owe their origin to submarine eruptions having 

 taken place after the trachytes had been completely formed. The 

 two rocks, although once in mechanical contact, are in no way con- 

 nected as to their mode of formation. The marine shells included 

 in the rhyolites make it probable that their eruption began contem- 

 poraneously with the deposition of Leithakalk, and ended with the 

 beginning of the Cerithium-beds (consequently before the eruption 

 of the basalts of Northern Hungary, which are frequently in contact 

 with rhyolites and include fragments of them), while the trachytes 

 may be supposed to belong to the Oligocene or even the Eocene 

 period. The varieties of rhyolite are : — 



a. Trachytic rhyolite, dark- coloured, porphyroid, passing into 

 perlite, sphaerulite, and white tufaceous rhyolite. This is the type 

 of original rhyolite before its chemical and physical alteration by 



* Bull. Soc. Gcol. de France, 2^^ serie, vol. xxiii. pp. 11-43. 



