1900-1901. | A Geological Trip. 169 
broken up by a powerful upheaval and then pushed together 
like a pack of cards. The outcrops of three main lines of 
thrust, the maximum thrust planes, have been traced, the trun- 
cated edges of which are shown by the three black lines on 
the map. The lowest one is named the Glencoul thrust, as it 
is extremely well developed on the banks of Loch Glencoul. 
The next in order is the Ben More thrust, and is well dis- 
played in the vicinity of Ben More of Assynt. The third 
thrust plane is called the Moine thrust, because it brings the 
Moine schists which lie to the east on to the top of the lime- 
stones in the Durness district. This thrust plane is well 
developed at the Knockan Cliff, a little to the south of the 
- village of Elphin, and can be traced all the way from Whitten 
Head in the north to beyond Ullapool. You will observe that 
at the Knockan Cliff the three great thrust planes appear to 
coalesce. 
Besides these three great maximum thrust planes there are 
others of less extent; for when the great movements took 
place the friction along the sole of the thrust caused the rocks 
more nearly concerned to break up and fold over one another, 
producing a complicated series of major and minor thrusts. 
To the east of the outcrop of the last great thrust plane lie the 
Moine schists over many miles of country. To explain the 
matter more fully, I have prepared the following diagrams 
(fig. 2, A, B, C, D), in which we shall trace roughly the build- 
ing up of the geological series in this district. Fig. 2, A takes 
us back to the time when the gneiss was the only rock in the 
place: here we see a section of it. It is usually supposed to 
consist of a great mass of eruptive rocks of a more or less 
basic type. These have been foliated by powerful mechanical 
movements within the mass, which was afterwards invaded 
by numerous dykes of molten matter and again subjected to 
great shearing and crushing movements. Here we see it at 
the surface, the sea and atmospheric influences together re- 
ducing it to a plane of denudation. This rock, where it 
appears at the surface, now produces a typical scenery. It 
forms rolling tracts of hummocky rock, mostly low-lying, as in 
Barra, but sometimes rising as high as 600 or 700 feet, as at 
Lochinver. The surface exposed by the old gneiss now is 
probably little different from that left by the old plane of 
