64 A CHAPTER IN THE PHYSICAL GEOGRAPHY OF THE PAST. 
Reade, “On the Origin of Mountain Ranges,” to which I must 
refer any of you who may wish to gain further information on 
the subject. 
These two theories, framed to account for the upheaval of vast 
thicknesses of strata deposited on old sea bottoms, are, in my 
opinion, not so antagonistic as they appear at first sight. I 
believe that further research will show that doth agencies, 2.e., 
secular contraction, and expansion of the sediments by heat, have 
had a hand in the work. 
In all highly folded mountainous districts we find that the rocks 
are bent in such a way as to indicate that the lateral force was 
exerted more on one side of the elevated region than on the 
other ; that the range in fact exhibits a “shoving” side and a 
resisting side. Our Pennine Range is no exception to this rule. 
On its western side, as indicated in our diagram, the corrugations 
and faulting are much more pronounced than on the eastern side 
in the colliery districts of North Derbyshire and South Yorkshire, 
where the inclination of the strata from the centre of the great 
anticlinal arch is much more even and regular. 
In order that you may have a due idea of the proportion of the 
Pennine folding to that of a lofty range like the Alps, I must 
refer you to the sections in the adjoining plate, drawn to a true 
scale of z35's09> both vertically and horizontally. 
You may now ask, at what period of the world’s history did all 
this folding of our English Carboniferous Rocks take place ? 
I need scarcely tell you that geologists cannot reckon by the 
ordinary standard of years and centuries. They can only refer 
geological occurrences to certain great periods coincident with the 
laying down of masses of strata, which for various reasons they 
are agreed to consider as belonging to one geological age. 
The strata which are found succeeding the Carboniferous Rocks 
in upward succession are known as the Permian, and it is mani- 
festly possible, by observing the position of these latter rocks 
relatively to the underlying Carboniferous, to ascertain if the great 
earth movements which produced the Pennine Anticlinal were 
anterior to the deposition of the Permian or swdseguent. If, for 
