the Mountains of Scotland. 123 
stories built up of the same materials as the basement, and the third 
formed of different materials. What is more extraordinary, but 
nevertheless appears to be certain (though I have seen but one 
example of it, and could not devote sufficient time to its examina- 
tion), is that the third story does not everywhere rest upon the 
second, but cuts across the latter obliquely so as to lie upon the first, 
or even immediately upon the basement. This is an extraordinary 
complication, of which other instances have not been recognized. 
Series of thrust planes, arranged one behind the other in échelon, 
and each producing horizontal displacements of several kilometres, 
are well known, notably in Provence. But each of these thrusts 
corresponds with a distinct fold; each one has its own domain, and 
does not trespass upon its neighbour’s. In Scotland one cannot 
resist the impression that one is face to face with a unique 
phenomenon, and that the division in three folds, each forming one 
of the three stories, is non-existent. 
There is, however, a difference still more important in my eyes; 
it is the absence of inverted beds. In the Alps and in Provence 
what characterizes these phenomena of horizontal movements is the 
more or less intermittent presence of beds succeeding one another 
in inverse order, the oldest above, the most recent below. These 
inverted beds are at the same time generally dragged out; that is 
to say, the normal thickness of the divisions is there very greatly 
reduced. It is these beds that seem to give the clue to the phenomenon 
and that have allowed Professor Heim to formulate his theory, 
comparing it to the unfolding of a fold, the base of which, forced 
to stretch over a larger area, undergoes a kind of rolling out. It 
would be very easy, it is true, to answer that in Scotland the dimi- 
nution in thickness has proceeded to zero; that the dragging out 
process has been carried on so as to become suppression, and the 
same mechanism can still be resorted to. But there is something 
further: above each thrust plane there are in Scotland also beds in 
an abnormal position, only this position is of quite another kind ; 
these beds are oblique to the thrust plane and are indefinitely repeated 
in consequence of a series of small faults with a hade a little larger 
than the dip of the beds. In other words, each of our three stories 
has a floor; but this floor, instead of being formed of planks parallel 
to the base of the story, is as if it had been formed by cutting these 
planks into slices obliquely uptilted. All these slices are similar 
among themselves, always sloping to the east, 7.e. towards the side 
whence the movement has come, and the beds are never inverted. 
The small separating faults are usually not very obvious, and con- 
sequently, finding similar beds recurring over large areas, without 
apparent horizons, and always dipping in the same direction, one 
would be led to attribute to them impossible thicknesses. It is here 
that the utility of the subdivisions introduced in the series becomes 
manifest: one is confronting a set of numbered beds, the numbers of 
which, though not very distinct, are yet well known and are every- 
where recognizable by minute examination. This examination has 
been carried out in an extraordinarily careful and conscientious 
