42 RELATION OF UNSTRATIFIEO 
Beneath the whole series of stratified rocks 
that appear on the surface of the globe (see 
section PI. 1), there probably exists a founda- 
tion of unstratified crystalline rocks ; bearing 
an irregular surface, from the detritus of which 
the materials of stratified rocks have in great 
measure been derived,* amounting, as we have 
stated, to a thickness of many miles. This is 
indeed but a small depth, in comparison with 
the diameter of the globe ; but small as it is, it 
affords certain evidence of a long series of 
changes and revolutions ; affecting not only the 
mineral condition of the nascent surface of the 
earth, but attended also by important alterations 
in animal and vegetable life. 
The detritus of the first dry lands, being- 
drifted into the sea, and there spread out into 
extensive beds of mud and sand and gravel, 
would for ever have remained beneath the sur- 
face of the water, had not other forces been 
subsequently employed to raise them into dry 
land ; these forces appear to have been the same 
expansive powers of heat and vapour which, 
having caused the elevation of the first raised 
portions of the fundamental crystalline rocks, 
* Either directly, by the accumulation of the ingredients of 
disintegrated granitic rocks ; or indirectly, by the repeated de- 
struction of different classes of stratified rocks, the materials of 
which had, by prior operations, been derived from unstratified 
formations. 
