42 L. Semann on Geological Phenomena in the Solar System. 
fusion of a metal, contains more vacant space in proportion to its 
volume than would be required in the globe for the absorption 
of its gaseous envelope ; it is scarcely possible that any crystal- 
line rock should be wanting in this slight degree of porosity. 
From the preceding considerations, the successive absorption 
of the air and water by the solid portions of the globe becomes 
in the highest degree probable, and we may conclude that our 
earth will one day present that same total absence of ocean and 
atmosphere which we now remark in the moon. It is evident 
that this progress of the waters towards the earth’s centre must 
have long been in operation, and it becomes interesting to con- 
sider the effect which this must have had upon the level of the 
ocean. Let us suppose that the rocks near to the surface of the 
earth contain one hundredth of water, a proportion which from 
inquiry is evident. 
I am convinced that the ultimate complete cooling of the inte- 
rior of the earth is inevitable. We may affirm on general princi 
les that between two media of different temperatures separated 
y alayer of rock which is a conducter of heat, an equilibrium 
will at length be established. It is probable that this cooling is 
however to a great extent, effected by the innumerable currents 
of water and gases which circulate in every direction through 
the sage of the globe, and of which volcanic eruptions, hot 
may wn 
heated much above its boiling point. The 
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