The Dolomite Mountains. 39 
which we may still obtain a good general notion of the physical 
structure of the region. The central chain or ‘axis’ of Plutonic and 
Metamorphic rocks—gneiss and syenite and granite—runs west and 
east, from Bormio and Glurns on the Stelvio, to the Glockner, and 
along the northern side of the valley of the Drave, passing by the 
silver-mines of Gmiind, and dividing into two branches as it ap- 
proaches Gratz. ‘This range is flanked by regions of old slaty rocks 
and calcareous beds (near Bleiberg) full of Producta Martini ; with 
zones of Trias and Alpenkalk, ‘ Quader’ and Hippurite limestone. The 
great escarpments of the limestone on either side of the Alps are found 
to face the central masses along the borders of which they run. 
The regularity of these zones is interfered with by the great beds 
of porphyry and volcanic tuff, which are older than the Trias. The 
porphyry forms enormous plateaux in the neighbourhood of Botzen, 
averaging 4,000 feet in elevation, intersected by narrow ‘cloughs’ 
whose walls rise 2,000 feet above the streams, with sometimes a 
stair-like outline. Above these is placed the tuff-plateau, 2,000 feet 
in thickness, and still higher by thousands of feet rise here and there 
the masses of Dolomite. 
The authors of the Memoir on the Eastern Alps supposed the 
Dolomites to be of Oolitic age; their serrated peaks are conspicuous 
in the sections accompanying the paper. They observed that at 
Bleiberg,* the metalliferous Dolomites rested on red sandstone and 
gypseous marls, but they were not aware that the overlying rock was 
older than the Lias. The geology of the district has now been more 
completely explored, and is graphically given in the work of Baron 
von Richthofen (4to. 1860, with geologically coloured map and 
sections), to which Mr. Churchill acknowledges himself indebted for 
the materials of his sketch. The order of succession of the Triassic 
beds may be briefly stated :— 
1. Lower Lias ; ‘ Dachstein’ (Dolomite). 
2. Upper Trias or ‘ Keuper;’ ‘ Raibl beds’ (fossiliferous), 
Schlern Dolomites, 83000—5000 feet thick. 
St. Cassian beds, a local member of the sedi- 
mentary volcanic tuff, 2,000 feet thick. 
Mendola Dolomite (with Ammonites globo- 
sus, &C.). 
3. Muschelkalk ; Campil beds, Seiss beds, &e. 
4. Bunter sandstein ; Groeden sandstone. 
The Lias forms plateaux, with the ‘Raibl beds’ at its borders. 
Sometimes these latter appear as sloping ledges on the perpendicular 
walls of unbedded Dolomite, and are again surmounted by a series of 
short escarpments of Lower Lias Dolomites, forming a ledge between 
the upper and lower precipices which resembles a ‘stratus’ cloud 
* The lead-mines of Bleiberg, near Villach, are the most extensive in Austria, 
yielding annually 1,600 or 1,700 tons of metal. The roof of the workings is 
formed of a dark brown marble, full of Ammonites, polished sections of which 
exhibit the most brilliant iridescence. This is the famous Lumachello, or ‘Fire- 
marble,’ 
