be
absolutely essential to the origin and development of the higher types
of terrestrial life, and that most of these must have been certainly
dependent on a very delicate balance of the forces concerned in the
evolution of our planet. Our position in the solar system appeared to
him to be peculiar and unique because, he thought, we may be almost sure
that these conditions do not coexist on any other planet, and that we
have no good reason to believe that other planets could have maintained
over a period of millions of years the complex and equable conditions
absolutely necessary to the existence of the higher forms of terrestrial
life. Therefore it appeared to him to be proved that our earth does
really stand alone in the solar system by reason of its special
adaptation for the development of human life.

Granting this, however, the question might still be asked, Why should
not any one of the suns in other parts of space possess planets as well
adapted as our own to develop the higher forms of organic life? These
questions cannot be answered definitely; but there are reasons, he
considered, why the central position which we occupy may alone be
suitable. It is almost certain that electricity and other mysterious
radiant forces (of which we have so recently discovered the existence)
have played an important part in the origin and development of organised
life, and it does not appear to be extravagant to assume that the
extraordinary way in which these cosmic forces have remained hidden from
us may be due to that central position which we are found to occupy in
the whole universe of matter discoverable by us. Indeed, it may well be
that these wonderful forces of the ether are more irregular--and perhaps
more violent--in their effect upon matter in what may be termed the
outer chambers of that universe, and that they are only so nicely
balanced, so uniform in their action, and so concealed from us, as to be
fit to aid in the development of organic life in that central portion of
the stellar system which our globe occupies. Should these views as to
the unique central position of our earth be supported by the results of
further research, it will certainly rank as the most extraordinary and
perhaps the most important of the many discoveries of the past century.

While still working on this section of his "Wonderful Century," he was
asked to write a scientific article, upon any subject of his own choice,
for the _New York In