The simplest hypothesis we can make concerning the Earth"s deep

interior is that the chief ingredient is iron; perhaps a full
half of the volume is iron
The simplest hypothesis we can make concerning the Earth"s deep
interior is that the chief ingredient is iron; perhaps a full
half of the volume is iron. The normal density of iron is 7.8,
and of rock formations about 2.8. If these are mixed, half and
half, the average density is 5.3. Pressures in the Earth should
increase the density and the heat in the Earth should decrease
the density. The known density of the Earth is 5.5. We know
that iron is plentiful in the Earth"s crust, and that iron is
still falling upon the Earth in the form of meteorites. The
composition of the Earth as a whole, on this assumption, is
very similar to the composition of the meteorites in general.
They include many of the metals, but especially iron, and they
include a large proportion of stony matter. Iron is plentiful
in the Sun and throughout the stellar universe. Why should it
not be equally plentiful in the materials which have coalesced
to form the Earth? It is difficult to explain the Earth"s
constitution on any other hypothesis.