Geology and Paleontology. 923 
centres of all cosmic spheres are of higher specific gravity than the 
surfaces. On the contrary, after solidification has taken place, by 
virtue of thermal radiation into the infinite of space, the high degree 
of internal heat tends, very considerably, to diminish the density of 
the interior. 
The complexity of this problem is not amenable to mathe- 
matic resolution. Even the elastic resiliency of the most persistent 
gases increases more rapidly than any assumed amount of pressure. 
Thus, if the pressure increases as the natural series 1, 2, 3, 4, ete., 
the elastic resilience is such that the resulting volumes are not 4, 4, 
, 4, etc., nor anything like it, except in the very lowest of the 
series. Still we are warranted in all cases in saying that the greater 
the pressure the greater the density for the same kind of matter. 
ow,a few words on the formation of a solid crust over a molten 
sphere are entirely pertinent. It has been held by some authors 
that no crust can form over such a sphere; for, say they, when the 
surface cools it is heavier than the molten mass within, and must 
necessarily sink ; so that the centre would become solid first. First, 
here is a palpable reductio ad abswrdam ; for this would necessarily 
result in cooling so as to solidify at the centre first. Can any 
rational mind accept this absurdity ? 
nd, ejected lavas always cool on the surface first, while yet 
the deeper portions are molten even so as to flow long after a solid 
crust has been formed. Thus does direct observation show the 
gold. Cold silicon can not sink in molten iron, Yet, all the lighter 
materials are on and form the outside of earth, and of every other 
sphere where they exist. Unless there may exist a cosmic sphere 
of pure gold or pure platinum, or something of that kind, their 
hypothesis can never be realized. : 
Fourth, these lighter materials are highly non-conductive to heat, 
and hence husband the internal heat most providentially ; so that 
earth will continue to have an internal heated core for raising 
mountains, continents, islands, etc., eons to come, as it thus far has 
had during eons past. 
Fifth, the dream of those other philosophers, that all the waters 
of all the oceans will disappear to the centre of earth, cannot be 
realized, unless the outer non-conductive materials are in excess of 
the heavier central materials, which the higher mean gravity of 
earth seems to contradict. 
Sixth, this fact of heavier central materials insures the molten 
condition of a portion of the centre, in spite of all contrary hypo- 
