Dr, Peters — On the Geology of the Dohrudscha, 63 



I should mention here, that the Chalk in this country is every- 

 where overlain by calcareous or sandy beds of Miocene age. The 

 metamorphosed masses consist of a green or greenish-grey soft 

 mineral, which contains many crumbling remains of a flint-like 

 silicious matter, the whole mixed with carbonate of lime. After 

 extraction by acetic acid, the dry substance becomes of a yellowish 

 colour. When analyzed by Dr. Richard Maly, it gave the following 

 composition : — 



Silica 56-11 Magnesia 240 



Alumina 26-21 Water 12-00 



Peroxide of Iron 1.77 



It is, therefore, essentially a hydrosilicate of alumina. Although 

 this mineral much more nearly resembles a chloropal poor in iron 

 than an allophane, the relation of the latter to the Kentish green- 

 coated flints is not so very distant but that we may suppose the 

 process of replacement and the chemical causes were nearly the 

 same in both instances, although occurring in such distantly removed 

 countries. 



My paper on the geological and geographical description of the 

 northern part of the Dobrudscha is published in the Transactions 

 of the Academy of Vienna (vol. xxvii.). 



The district between the Danube and the Black Sea, known as 

 the Dobrudscha, offers many interesting points in its geological 

 constitution. 



The drift-deposits of Bulgaria and Bessarabia correspond v^ith 

 the Hungarian " loess," forming vast undulating plains, which attain 

 a height of from 400 to 500 feet above the sea. 



The freshwater deposits of Bessarabia, characterized by Dreissena 

 polymorpha and many Cardium-like shells, intermixed with some 

 species well-known in the Austrian loess and recent deposits, are 

 not of Miocene age as Capt. Spratt has supposed, — they are rather 

 truly intercalated in the land-shell marls or loess. This Dreissena- 

 bed probably belongs to the oldest drift-series joining (in the Pontic 

 regions) the upper marls with the true Miocene freshwater deposits, 

 called the " Congeria-beds " by the Austrian geologists, and well 

 characterized by many large species of Dreissena or Congeria, and 

 Cardium. These beds have been observed in many parts of Bulgaria 

 and Wallachia. A Miocene limestone, wholly formed by Tapes gre- 

 garia, some species of Cardium, Buccinum, Troclius, and a multitude 

 of Foraminifera, belongs to the " Sarmatic formation" of Mr. Suess, 

 without a trace of the older Mediterranean or Indian shells. 



The Chalk corresponds, by the presence of Belemnitella mucronata, 

 Ostrea vesicularis, and some Foraminifera, with the Chalk of Meudon. 

 A Turonian division probably exists. A yellowish marl, from five 

 to six hundred feet in thickness, occurring in the Babadagh moun- 

 tains, and many banks along the coast, with remains of Ostrea and 

 Inoceramus {Cripsii f) but not containing any Eudistes, appears to 

 belong to it. Of the Upper Jurassic beds, a part, containing Diceras, 

 Pteroceras oceani, and some species of Nerinea, resembles the Kimme- 

 ridge Clay of Besan9on, and part containing numerous Terebratulce, 



