ORIGIN OF THE DIAMOND 383
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mud. It has been said that the sharp edges of the diamond crystals
found in the kimberlite would be impossible had they been formed in a
molten mass, but as Moissan produced such diamond crystals, though
small, from charcoal confined in fused iron, and diamond will not burn
without a free supply of oxygen, the argument appears invalid.
Geologists
assert that the center of the earth is solid, but that between the
crust and that solid center, lies a mass of molten material. They also
claim to have indubitable evidence that the earth's bulk is gradually
shrinking, while at the same time by astronomical forces it assumes a
somewhat elliptical form at the equator. In the process of shrinking,
the uneven thickness and strength of the crust would produce uneven
results. Some weaker parts of the area would settle lower, toward the
center of gravity, leaving other stronger parts elevated above the
general level, and they would become, thereby, mountain ranges where
the buckling occurred, and high plateaus, if the area was large, within
the mountainous border lines of greatest strain, marking the junction
of the weaker sinking portions of the crust and the thicker and more
stable part.
It
seems reasonable to suppose that some such occurrence took place
during past ages in South Africa, whereby the earth's crust seaward,
east, west, and south from the mountains surrounding the diamond
plateau, sank, leaving the plateau at an elevation, with undisturbed
horizontal strata, except for occasional vertical rents in it extending
probably to the underlying magma. This hypothesis seems more probable
than that of a deep explosive or expansive force sufficiently extensive
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