THE FIRST (CHAPTER OF, THE GEOLOGICAL RECORD. 355 
to enable many of the lower organisms to exist ; upon it or 
rather it should be said, in its ocean, for as yet we only recog- 
nise the earth as a sphere externally coated, as it were, with a 
uniform sheet of water. Certain changes have, however, been 
going on in the solid crust of the earth which here demand our 
consideration since they tended to completely revolutionise its 
external features as well as prepared the way for its future 
career. In the first place as soon as the stony cpust had com- 
pletely consolidated over the molten nucleus within, it would 
present itself with a comparatively uniform and smooth surface 
externally, when, however, this crust increased in thickness and 
became colder, contraction would take place in its mass, which 
would result in the production of cracks and fissures in the 
crust itself, the sides of which, becoming dislocated, would 
bring about elevations and escarpments to interrupt the 
previously regular contour of the sphere, whilst by the subsi- 
dence of portions, some of the still fluid rock below would be 
forced up along the lines of such fissures and so form dykes of 
eruptive rock traversing the original crust. All these effects 
would, however, be immensely augmented, when the exterior 
had so far cooled down as to be covered with the ocean, since 
then, owing to such fissures allowing the water to penetrate 
down to the molten mass within, internal forces would be called 
into play, giving rise to volcanic phenomena which would result 
in the elevation of mountains, and the upheaval of islands and 
continents, thus forming the first dry land on the surface of the 
earth. 
Instead of the previous uniform sphere we should now have 
its surface varied by elevations and depressions, valleys and 
mountain ranges, which by giving direction to the movements 
of the salt water in the ocean, and the fresh water from the 
heavens, by which the lakes and rivers are supplied, would at 
last set in action those external or secondary forces which have 
played so important a part in modifying the outward configura- 
tion of our globe and the distribution of organic life over its 
surface. 
The primitive crust of the earth thus ruptured, along with 
the mineral matter ejected from below as before described, 
would now become still further broken up and pulverised by the 
mechanical force of water, powerfully assisted by the decompos- 
ing action of the great excess of carbonic acid gas present in 
the atmosphere of this period, and would in process of time 
become so comminuted as to allow of the particles being carried 
off and sorted by the action of rivers and the sea, which would 
deposit them as sedimentary beds of varying character. It 
should however be remembered that the exact mineral compo- 
sition of the original crust of the earth must ever remain an 
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