l8o TRANSACTIONS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
north-eastern Grampians, as was long ago pointed out by Nicol, 
these rocks have a dominant north-west dip, and seem to pass under 
the mica-schists, quartz-schists, and limestones of Loch Tay, which 
again pass upwards into the quartzites of Schiehallion and Glen Lyon. 
Sir A Geikie, in his Presidential Address to the Geological Society 
for 1891, already cited, notes the remarkable lowness of the dips in 
this region and also adopts the view that these slates, phyllites, and 
grits pass under and are older than the more crystalline rocks lying 
farther to the north. So far as we have been enabled to observe 
there is no evidence of any stratigraphical break or overthrust be¬ 
tween the quartz-schists and mica-schists of Loch Tay on the one 
hand, and the grits, shales, and phyllites of Callander, the Pass of 
Leny, Crieff, Comrie, and Dunkeld on the other. On tracing these 
rocks,^ however, towards the south-west, as was also shown by Nicol, 
the dips become gradually higher and higher towards the extreme 
south-western boundary of Perthshire, as at Aberfoyle. They have 
still, however, a north-westerly dip at this point, evidently passino- 
under the limestones and schists of Glen Dochart, and thus bearino- 
the same relationship to these schists as was seen to hold good in 
the last locality. ^ On reaching Loch Lomond they become vertical, 
and from this point, along the shores of the Firth of Clyde, the dip is 
reversed, it now being towards the south-east, as at Dunoon and 
along the shores of Cowal, and thus they now, apparently, overlie 
the rocks forming the interior of the Highlands. The relationship 
of this marginal belt of grits, greywackes, and phyllites to the main 
mass of the Grampians, and its structure, may be seen in the 
section from Kirn to the head of Loch Eck. Along the shores of 
Cowal these rocks are seen to dip, at angles varying from 40 to 70 
degrees, to the south-east. Near Kirn pier, a series of beds of 
phyllites, greywackes, and black slates are seen interbedded with 
bands of limestone. Continuing the section up the Holy Loch, a 
great series of beds of lustrous phyllites, still dipping towards the 
south-east, may be observed. Near the head of the Holy Loch, they 
pass upwards into^ a more arenaceous group of grits and greywackes, 
having at this point a dip of 55 deg. to the south-east. Proceedino- 
up Loch Eck some fine sections of these arenaceous rocks may be 
seen, evidently greatly disturbed, but still dipping towards the south¬ 
east. 
We have already shown how Nicol was confronted with the pro¬ 
blem of the relationships of these rocks, and how he decided in 
favour of the slates and phyllites being the younger rocks. He also 
believed that they were in their normal position, relative to the mica- 
schists of the interior, along the Firth of Clyde, while in the north¬ 
east, as in Perthshire, they had been faulted against these schists and 
