310 
THE PHYSICAL GE0GR4PHY OF THE PAST. 
As the great geosynclinal bends more and more down¬ 
wards, the first formed and lowest strata are carried through 
zone after zone of constantly increasing temperature, which 
at last is sufficient to melt, or at any rate to soften, the 
deepest part of the inverted arch. The very keystone of the 
arch is then gone, and it is unable to withstand the great 
lateral strains due to the secular contraction of the earth, 
and forthwith the elevation of the mass begins. 
On the second hypothesis, the lateral pressure which has 
brought about the folds and wrinkles in the earth’s crust is 
attributed to the expansion of the mass of sediment when it 
is carried into the zones of higher temperature, as the 
geosynclinal, or great earth trough, bends more and more 
downwards under the weight of the superincumbent strata. 
This hypothesis has, within the last year or so, come into 
more prominence, owing to the appearance of a most 
suggestive work, by Mr. Mellard 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 both 
agencies, i.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 oil 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 inclina¬ 
tion 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 foldiug 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 j 3 ^ooo> 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 
