Vol. 50.] GNEISSES IN THE COTTIAN SEQUENCE. 255 



inclined to the north, and is overlain by mica-schists which form the 

 2051-metre point north of the col; the band thence rises, and is 

 succeeded by masses of dolomite intensely folded and contorted and 

 with beds of 'pietre verdi,' probably of a clastic origin, caught in 

 between the limestone masses. The beds here strike 35° N. of W., 

 while the thrust has come from approximately W. by S. Along 

 this ridge, in spite of the intense foldings of the rocks, there is little 

 evidence of any definite schistosity, and the actual summit of Rocca 

 Bianca (2379 metres) is of a rock with foliation so imperfect that in 

 the field we called it a micaceous grit; judging, however, from the 

 great extent to which the quartz-grains are seen to be corroded, when 

 examined under the microscope, this rock is probably a quartz- 

 porphyry. South of the Colletta Bianca the rocks become more 

 schistose and belong to the 'pietre verdi' series with numerous quartz- 

 veins. The summits of Cima del Liste and Punta Bruta, however, 

 mark a return to a less foliated series, being formed of a micaceous 

 grit or schist breaking into large flat slabs, with a general strike 

 north and south, at one place working to 10° E. of JST. ; the dip is 

 13° west. Farther south the strike is 10° W. of IN"., with a westerly 

 dip of 16°. Associated with these evenly-foliated schists there are, 

 on the south face of Punta Bruta, some interstratified thin green beds 

 which probably represent layers of volcanic ash. There are also 

 numerous blocks of a green rock in the same schists ; they range 

 from about lg to 3 feet in length, and in their present form are 

 lenticular ; the long axes are in the plane of foliation, the lines of 

 which bend rouud the blocks. Microscopic examination shows 

 them to consist of garnets, chlorite, tremolite, and epidote ; they 

 represent altered blocks of a basic igneous rock, and their asso- 

 ciation with what is possibly a bed of volcanic ash led us in the 

 field to consider the possibility of their being ejected blocks. The 

 microscopic evidence neither confirms nor conclusively disproves this 

 hypothesis. 



In many places along this ridge between the Bocca del Cavalupo 

 and Punta Cornour the rocks are either not foliated, or the foliation., 

 such as it is, is coincident with the bedding ; this is probably the 

 case also with the rock which includes the eclogite-blocks. In tne 

 ' roches moutonnees ' around Lagho d'Envoi, a charming little lake 

 in a glaciated rock-basin, we have clear evidence that such is not 

 always the case, as the vein there has been intensely contorted, 

 before the foliation of the rocks ; the foliation here has the normal 

 strike of 10° W. of INT., with a westerly dip of 10°. Around the Hanks 

 of Capello d'Envoi the schists become coarser and the limestones 

 are schistified. 



Evidence for the same independence of the foliation and stratifi- 

 cation is seen in the view of Punta Cornour from Tredici Laghi. A 

 massive bank of white rock (probably dolomite) may be observed 

 interstratified between masses of the ' pietre-verdi ' series ; the white 

 rock dips to the west, but the foliation dips much more sharply and 

 crosses the bedding at a high angle. 



Near the summit of Punta Cornour, the large garnets and the 



