BY H. I. JENSEN. 539 



(1) Older basalts and nepheline basalts. 



(2) Tephrites poor in Mg. 



(3) Essexites. 



(4) Phonolites very poor in Mg and Ca. 



(5) Trachyte very poor in Mg and Ca. 



This area therefore affords a very complete series of alkaline 

 rocks. The mass lies to the south of the German area of Mesozoic 

 sedimentation, and is situated on the flanks of the Bohemian 

 massive. 



The volcanic range of the Siebengebirge in the Rhenish pro- 

 vinces occupies a similar position where the Mesozoic sediments of 

 North west Germany (Gres bizarres and Yosgian Grits) have 

 been folded and faulted against the Black Forest and Vosgian 

 horsts. The lavas here too are of Tertiary age. 



The early Tertiary intrusive bosses and lavas of Banat occupy 

 a closely analogous position, being situated on a N.N. E. to 

 S.S. W. fault-line east of which there is a vast Mesozoic basin, 

 and to the west the ancient massive of South-west Hungary and 

 Croatia (mica schist, etc.). 



The Banat igneous rocks are to a great extent alkaline (tra- 

 chytes, etc.). (See ' La Face de la Terre,' Ed. Suess, Tome. i. 

 p.209). 



7. Mountain- Masses of Transylvania. — On a continuation of 

 the great Carpathian line of folding and faulting to the south we 

 find the mountain-masses of Transylvania. Here great intrusions 

 of nepheline syenite have taken place, as at Ditro, and great lava 

 flows of trachyte as in the range of l'Hargitta.* This alkaline 

 series is continued into Boumania and Moldavia, where similar 

 rocks occur at Dobrogea.f The situation of these rocks is 

 analogous to those already mentioned, since they have the Servian- 

 Balkan massive to the west, and the area of Mesozoic sedimenta- 

 tion to the east. Whether the syenites of the Balkan mountains 

 are related to the alkaline group has not yet been determined. 



* Suess, ' La Face de la Terre, Vol. i. p. 634.' 

 t Murgogi, ' Genesis of Riebeckite,' Amer. Journ. of Science, Vol. xx. 

 Aug. 1905. 



