1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 167 



group is first clearly exposed with the dark grey or blackish *' Halo- 

 bian" sandstone, rising out from beneath the dolomitic rocks of the 

 Heilige-Kreutz, and then is exhibited in several flexures along the 

 sides of the gorge which leads to St. Martin. In this gorge, particu- 

 larly near Poderova, vertical walls of muschelkalk throw off red marls 

 occasionally gypseous, and pebbly conglomerates with many curvatures 

 and flexures ; the red ground being usually interlaced and associated 

 with limestones. Lastly, the system is flanked to the north of St. 

 Martin by crystalline schists (here very micaceous) which occupy the 

 place of the transition and metamorphic rocks of the Central Tyrol, 

 and range to the left bank of the river Rienz ; for, on the right bank 

 of this stream near Sonnenburg is seen the western end of one of the 

 finest of Leopold von Buch's so-called ellipsoids of granite, the eastern 

 extremity of which constitutes the striking Iffiger Spitz near Meran. 

 The protrusion and juxtaposition of this grand mass of granite ac- 

 counts, indeed, for the highly crystalline condition of the schists 

 between it and the trias. 



Trias of Recoaro and the adjacent t7'acts. — Between the zone of 

 trias which occupies the valleys of Grodner, St. Cassian, &c., and 

 the southern edge of the Tyrolese Alps, there are other ellipsoids of 

 crystalline rock, which in their elevation have exposed considerable 

 thicknesses of sedimentary deposits around them. The chief of these 

 is the Cima d'Asti with its central granite and its accompanying 

 crystalline formations in the Val Sugana, which I traversed rapidly 

 ou a former occasion. Further to the S.S.W. are other elhptical 

 masses, as seen in the valleys of Leogre, Posina and Recoaro, which 

 exhibit fundamental rocks of mica schist covered by an ascending 

 series, in which the trias is the prominent formation. By the valley 

 of Recoaro, I do not simply mean the gorge in which the baths 

 and village of that name are situated, but also all the undulating 

 district embracing Rovegliano and Communda, as well as both sides 

 of the ** Valle de Signori," on which the road from Schio and Rovereto 

 proceeds by the pass of Corneto * . He who has but little time at his 

 disposal may rest satisfied with the very clear exposition of the triassic 

 strata which are exposed on the side of the Spitz mountain, imme- 

 diately south of the village of Recoaro ; where ascending from a base 

 of mica or stea-schist traversed by trap dykes, some of which run 

 almost horizontally with the strata, the observer will recognize the 

 following ascending order, as exposed in the annexed woodcut (fig. 1). 



Some doubt may exist as to the age of the bottom stratum (2) rest- 

 ing on the mica schist (1). It is a red and white spotted, micaceous 

 sandstone with patches of coaly matter and carbonized vegetables, and 

 some geologists may be disposed to consider it carboniferous. But it 



* Having walked over this district by the mountain tract from the Corneto 

 Pass to Recoaro, I afterwards revisited it, as well as the adjacent districts of the 

 Venetian Alps, in company with the chief members of the Geological Section of the 

 "Venetian meeting of the " Scienziati Italiani," including not only my previous com- 

 panions Von Buch and De Verneuil, but also the Marchese Pareto, M. de Zigno, 

 Major Charters, M. Parohni, and Mr. Pentland. M. Trettenero explained the 

 details at llecoaro, and M. Pasini became our leader in the region around Schio 

 and in the Setti Communi, of Avhich hereafter. 



