were just the slag from the great furnace of his mind, slag not always
worthless. Brilliant and far-reaching as were his conclusions, he did
not execute a well-ordered plan. Rather he grew with his work, and his
work and its problems grew with him. He took a mountain-top view of
things, kept his eyes always on the far horizon, and in the splendid
sweep of his scientific conceptions sometimes overlooked the details
near at hand. Herein lay his greatness and his limitation.

These facts brought the writer face to face with a serious problem.
Ratzel's work needed to be tested, verified. The only solution was to go
over the whole field from the beginning, making research for the data as
from the foundation, and checking off the principles against the facts.
This was especially necessary, because it was not always obvious that
Ratzel had based his inductions on sufficiently broad data; and his
published work had been open to the just criticism of inadequate
citation of authorities. It was imperative, moreover, that any
investigation of geographic environment for the English-speaking world
should meet its public well supported both by facts and authorities,
because that public had not previously known a Ritter or a Peschel.

The writer's own investigation revealed the fact that Ratzel's
principles of anthropo-geography did not constitute a complete,
well-proportioned system. Some aspects of the subject had been developed
exhaustively, these of course the most important; but others had been
treated inadequately, others were merely a hint or an inference, and yet
others were represented by an hiatus. It became necessary, therefor, to
work up certain important themes with a thoroughness commensurate with
their significance, to reduce the scale of others, and to fill up
certain gaps with original contributions to the science. Always it was
necessary to clarify the original statement, where that was adhered to,