1821.] and adjoining Farts of the Continent. 459 



on the south of Clausen ; and covered by the same conglomerate 

 and by new red sandstone, on the south of Botzen, from Neu 

 Markt, in the Valley of the Adige, to Cavalese, in the Valley of 

 the Avisio. 



Along this line the porphyry seems to pass insensibly into the 

 conglomerate, each containing occasionally subordinate masses 

 of the other, and both presenting features which seem to induce 

 us to refer them to a contemporaneous origin ; i. e. to consider 

 the porphyry a crystaUine form of the same matter which, in its 

 coarser state, constitutes the red earthy cement of the pebbles 

 composing the conglomerate. 



This conclusion is borne out by similar phenomena in the same 

 formation in England, Scotland, and Ireland. 



V. Transition Rocks {proper li/ so called). 



Transition rocks, identical in every respect with the grey- 

 wacke and greywacke slate of England and Germany, occur 

 abundantly in the upper part of the Valley of Glarus, lying 

 beneath, and possessing very different characters from the new 

 red sandstone and conglomerate beds which are usually, but 

 improperly, called transition rocks. 



The slate quarries of Blattenburg, well known for their fossil 

 fish, lie in a calcareous variety of this greywacke slate, which 

 alternates with decided granular greywacke. The same transi- 

 tion formation extends from thence to the Valley of the Tamina, 

 above the baths of Pfeffers, and the mountains that flank each 

 side the Rhine for 10 miles north of Coire, where also the slate 

 frequently becomes calcareous. 



M. Brochant, in his paper on the Tarentaise and Upper Dis- 

 tricts of the Iserre, in Savoy, has described with much accuracy 

 a considerable extent of similar transition rocks on the south- 

 west of Mont Blanc, passing from fine greywacke slate through 

 various kinds of greywacke to coarse conglomerates, some con- 

 taining calcareous, others siliceous and granitic fragments. 

 Coeval and connected with the latter is the famous conglomerate 

 of the Vallorsine described by De Saussure, being a pudding- 

 stone of the highest antiquity, v/ith fragments of gneiss, granite^ 

 and clay slate : these transition conglomerates alternate with 

 micaceous slate, serpentine, and quartz rocks ; and are totally 

 ■different in appearance, as well as antiquity, from the new red 

 sandstone conglomerate of Schwanden. 



We have analogous formations in this country in the conglo- 

 merates which in Pembrokeshire and near Killarney • alternate 

 with greywacke and greywacke slate. The old red sandstone 

 of England is nearly connected with these last mentioned con- 

 glomerates, being intermediate between them and the mountain 

 hmestone, and separated by no strong line from the greywacke 

 formation, to which it is considered as belonging whenever it 

 occurs on the Continent. 



