460 Prof, Buckland on the Structure of the Alps, [June, 



P limit ive Rocks, 



Of the primitive rocks that form the central axis of the Alps, 

 I have only to remark at present, that in consequence of the 

 transition rocks being in many places totally wanting, they often 

 come into immediate contact with the secondary strata. 



J^ap Rocks. 



There are no traces whatever either of trap rocks, or whia 

 dykes, in the Alps of Savoy, Switzerland, or Tyrol, along the 

 entire north side of the great primitive riuge from Mont Blanc 

 to Presburg. But on the south side of it in Tyrol they occur in 

 considerable force at the Val di Fassa on the east of Botzen 

 under circumstances of singular resemblance to the trap rocks 

 and whin dykes of Scotland, and the north of Ireland. 



An excellent mineralogical account of this district has been 

 given by Prof. Brocchi, of Milan. The trap protrudes itself 

 through primitive rocks, new red sandstone, and Alpine lime- 

 stones, both in the form of small dykes and irregular masses : 

 the latter swell into mountains of great elevation at the upper 

 extremity of the Val di Fassa, above Vigo ; and in the Sieger 

 Alp close adjoining. They abound in well crystallized minerals, 

 chiefly of the zeolite family, which bear a strong resemblance 

 to those of the neighbourhood of Glasgow. In both countries 

 also the rock itself comes much into contact with, and cuts 

 through strata of, the new red sandstone formation. A similar 

 mass of trap occurs also cutting the Alpine limestone of Monte 

 Baldo on the Lago di Garda, where it is remarkable for contain- 

 ing veins and nodules of the green earth of Verona, a substance 

 which probably derives its colour, if not origin, from the decom- 

 position of pyroxene. 



Not far south from Fassa, on the border of the plain of Lom- 

 bardy, is a still more extensive formation of trap, which occupies 

 large tracts in the Vicentino, the Monte Berici, and Euganean 

 Hills. 



In these districts, basaltic dykes cut through rocks of all ages, 

 from the mica slate of Recoaro to the Calcaire Grossier of 

 Monte Bolca and the Monte Berici ; and amorphous masses of 

 trap protrude themselves into and through these same forma- 

 tions, so as to appear in different points both to he under and 

 over, and to alternate with them all. In the Euganean Hills, 

 the trap has been said to coHtain marine shells; and hence an 

 argument has been taken against its igneous origin. But these 

 remains occur only in a species of basaltic tuf, or regenerated 

 trap being a conglomerate rock composed of minute fragments 

 of trap, mixed with marine shells of the same character with 

 those that fill the strata of Calcaire Grossier with which these 

 trap conglomerates alternate. Similar shells are found on the 

 south of Turin at the base of the Sub- Apennines in a breccia 



