` 
Hurroy.—On the Formation of Mountains. xxxiii 
generally associated with metamorphic and granitic rocks. These have been 
formed by heavy argillaceous deposits, causing subsidence and contortion, 
which have been subsequently elevated by the superposition of calcareous 
beds. The second kind, of which the Andes may be taken as the type, are 
composed of nearly horizontal strata, generally associated with volcanic rocks.* 
These have been formed by the upward pressure of the underlying rocks 
caused by the subsidence of adjoining areas, and owe their height partly to 
this upward pressure, but often in great part to the overflowing of the super- 
heated rocks on the surface. 
There is, however, one other point that ‘has still to be taken into account. 
Tf we calculate the mass of the ocean we shall find that it is sufficient, if the 
surface of the earth were level, to cover it entirely to a depth of at least two 
miles. Now, if it is true that the earth has been formed by the slow conden- 
sation of gaseous matter, we can see no possible reason why any of the gaseous 
materials should be confined in the interior solidifying portions, and by their 
attempts to escape cause eructations, or bubbles that could raise any part of the 
- solid mass more than two miles high. In other words, I do not see how there 
could be any boiling or swelling up sufficient to form land above the surface of 
the ocean. If then there was no land in this primeval ocean for denudation 
to act upon, what was it that first disturbed the equilibrium of the crust and 
so led the way to those stupendous changes that we know have since taken 
place? But one answer can I think be given to this question, viz, the origin 
of life. Chemists are agreed that carbonate of lime was in solution in this 
primeval ocean, and when life, or rather life capable of secreting carbonate of 
lime, appeared it would abstract this substance out of the ocean and deposit it 
on particular areas, and thus, by disturbing the equilibrium, would prepare the 
world to be the habitation for those countless myriads of organised beings 
which now swarm over it. 
Į will hazard one more supposition. Over this primeval ocean the winds 
must have swept with great regularity, and currents must have followed in 
their wake. Now these currents would naturally take two directions, one 
N.E. and S.W., and the other at right angles to it. If, therefore, we suppose 
life to have originated at any one point, it would gradually spread in a 
N.E. and S.W., or N.W. and S.E. direction, and the first calcareous deposits, 
and consequently the first land, would take these directions also. This would 
give the direction of other deposits, and although much obliterated by the 
complications that have since taken place, we can possibly, even now, trace in 
the directions of our mountain chains some remnant of this primeval arrange- 
ment. But this is sheer speculation. 
* See also Darwin ‘‘On Volcanic Phenomena in South America.”—Trans. G. Soc. 
2nd Series, V., 601. 
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