12 A. Giekie—Crystalline Rocks of the Scottish Highlands. 
western fronts, until they are disrupted and the eastern limb is 
pushed westward. By a system of reversed faults, a group of 
strata is made to cover a great breadth of ground and actually 
to overlie higher members of the same series. The most extra- 
ordinary dislocations, however, are those to which for distinc- 
tion we have given the name of Thrust-planes. They are 
strictly reversed faults, but with so low a hade that the rocks 
on their up-throw side have been, as it were, pushed horizon- 
tally forward. The distance to which this horizontal cba aes 
ment has reached, is almost incredible. ° urn for ex 
ample, the overlying schists have “hang been shea west- 
ward across all the other rocks for at least ten miles. In fact, 
these thrust-planes, but for the clear evidence of such sections 
as those of Loch Eribol]l, could not be distinguished from 
ordinary stratification- planes, like which they have been pli- 
cated, faulted, and denuded. Here and there, as a result of 
denudation, a portion of one of them appears capping a hill- 
top. One almost refuses to believe that the little outlier on the 
summit does not lie normally on the rocks below it, but on a 
nearly yeaa! fault by which it has been moved into its 
lace. Masses of the Archean gneiss have thus been thrust 
up through the ies rocks and pushed far over their edges. 
When a geologist finds vertical beds of gneiss overlying gently 
inclined sheets of fossiliferous quartzite, shale and limestone, 
e may be excused if he begins to wonder whether he himself 
is not really standing on his bed 
The general trend of all these foldings pe ruptures is from 
north-northeast to south- -southwest, and th e steep westward. 
fronts of the folds show that the terrestrial movement came from 
east-southeast. Corroborative evidence that this was the direc- 
tion of the movement is furnished by a series of remarkable in- 
ternal rearrangements that have been superinduced upon the 
rocks. Throughout the whole region, in almost every mass of 
rock, altogether irrespective of its lithological characters and its 
structure, striated planes may be noticed which are approxi- 
mately parallel with the thrust-planes, and are covered with a 
fine parallel lineation, running in a west-northwest and east- 
southeast direction. These surfaces have evidently been pro- 
duced by shearing. Again, many of the rocks near the thrust- 
planes, and for a long way above them, are marked by a pecu- 
liar streaked structure which reminds one of the fluxion-lines of 
an eruptive rock. The coarse. pegmatites in the gneiss, for ex- 
ample, as the ey come within the apache ne the shearing, have 
of a rhyolite in which fluxion- structure has been nsec 
well developed. The gneiss itself coming into the same power- 
