the effect of a more tremendous force exerted at a lower depth in the
earth, and generally acting in lines pervading a considerable portion
of the earth's surface. We shall by-and-by see that the protrusion
of some of the mountain ranges was not completed, or did not stop, at
that period. There is no part of geological science more clear than
that which refers to the ages of mountains. It is as certain that
the Grampian mountains of Scotland are older than the Alps and
Apennines, as it is that civilization had visited Italy, and had
enabled her to subdue the world, while Scotland was the residence of
"roving barbarians." The Pyrenees, Carpathians, and other ranges of
continental Europe, are all younger than the Grampians, or even the
insignificant Mendip Hills of southern England. Stratification tells
this tale as plainly as Livy tells the history of the Roman republic.
It tells us--to use the words of Professor Philips--that at the time
when the Grampians sent streams and detritus to straits where now the
valleys of the Forth and Clyde meet, the greater part of Europe was a
wide ocean.

The last three systems--called, in England, the Cumbrian, Silurian,
and Devonian, and collectively the palaeozoic rocks, from their
containing the remains of the earliest inhabitants of the globe--are
of vast thickness; in England, not much less than 30,000 feet, or
nearly six miles. In other parts of the world, as we have seen, the
earliest of these systems alone is of much greater depth--arguing an
enormous profundity in the ocean in which they were formed.



SECONDARY ROCKS. ERA OF THE CARBONIFEROUS FORMATION. LAND FORMED.
COMMENCEMENT OF LAND PLANTS.