NICOL SOUTHERN GRAMPIANS. 



183 



more arenaceous or less crystalline, and the dip declines to 55°, 45°, 

 and even to 30°. On the east side of the loch, near Shandon, some 

 beds of clay-slate appear; and the strata, dipping first north at high 

 angles, then south, then again north, and finally regularly south-east, 

 show that in this place there is probably a faulted synclinal. The 

 same irregularity, as shown in the section, occurs on the west side 

 of the loch, but beyond this break the beds have a uniform south- 

 east dip to the clay-slate near Koseneath. These slates dip at 40° 

 to S. 35° E., and appear to consist, as in Bute, of two divisions, the 

 lower micaceous or talcose, and of a deep blue or purplish tint, the 

 upper of a lighter blue or green with a more silvery lustre. Some 

 of the beds resemble a fine-grained greywacke. This section and 

 that of Bute show what may be considered the regular normal order 

 of the formations on the south border of the western Grampians. 

 First, towards the axis of the chain, the more highly crystalline and 

 contorted mica-slate, covered by less crystalline and more even beds 

 of the same rock, and these in turn by talcose or chloritic blue and 

 green clay-slates, with occasional beds of greywacke. The low and 

 regular dip of the beds, and the conformity of the order to the only 

 theory of metamorphic action which seems admissible in the present 

 state of geological science, induce me to regard this as the true nor- 

 mal order of these formations. 



5. Loch Lomond. — The next section I shall notice (fig. 2) is that 



Fig. 2. — Section on Loch Lomond. 



N.W. 



Ben Lomond. Rowardennan. Sallachie. Auchmar. 



S.E. 



Mica-slate. 

 a. Syenite. 



Clay-slate. 



b. Granite. 



Balmaha. 



b c Old Red 

 Sandstone. 



c. Limestone. 



seen on the east side of Loch Lomond, from Ben Lomond to the 

 Red Sandstone at Balmaha, about ten miles east of the one just 

 described. 



Ben Lomond, at the northern extremity, consists of mica-slate, 

 often quartzose, much contorted, and dipping at low angles, and inter- 

 sected by veins of felspar-porphyry. Near Rowardennan the strata 

 become more regular, dipping at high angles (80° to 85°) to S. 27° E. 

 The rocks are still chiefly mica-slate, passing occasionally into a light- 

 grey talc-slate. About a mile below the inn some of the beds dip 

 north at high angles, and are intersected by a parallel vein of fine- 

 grained syenite, composed chiefly of red felspar and dark-green horn- 

 blende. At Sallachie Wood a coarse greywacke, very hard and full 

 of quartz-veins, appears, dipping at 80° to S. 27° E., and thus con- 

 formable to the mica-slates on the north. It contains distinctly 

 rounded grains of quartz, thus leaving no doubt of its mechanical 

 origin. Further on, the clay-slate, well exposed in the quarries, 



