will see America across the Atlantic and Japan across the Pacific; but
you cannot see, in one single effort of the imagination, an Atlantic of
empty blue water stretching to an empty horizon, another beyond that
equally vast and empty, another beyond that, and so on until you have
spanned the thousand horizons that lie between England and America. The
mind, that is to say, works in steps and spans corresponding to the spans
of physical sight; it cannot clear itself enough from the body, or rise
high enough beyond experience, to comprehend spaces so much vaster than
anything ever seen by the eye of man. So also with the stretching of the
horizon which bounded human knowledge of the earth. It moved step by
step; if one of Prince Henry's captains, creeping down the west coast of
Africa, discovered a cape a hundred miles south of the known world, the
most he could probably do was to imagine that there might lie, still
another hundred miles farther south, another cape; to sail for it in
faith and hope, to find it, and to imagine another possibility yet
another hundred miles away. So far as experience went back, faith could
look forward. It is thus with the common run of mankind; yesterday's
march is the measure of to-morrow's; as much as they have done once, they
may do again; they fear it will be not much more; they hope it may be not
much less.

The history of the exploration of the world up to the day when Columbus
set sail from Palos is just such a history of steps. The Phoenicians
coasting from harbour to harbour through the Mediterranean; the Romans
marching from camp to camp, from country to country; the Jutes venturing
in their frail craft into the stormy northern seas, making voyages a
little longer and more daring every time, until they reached England; the
captains of Prince Henry of Portugal feeling their way from voyage to
voyage down the coast of Africa--there are no bold flights into the
incredible here, but patient and business-like progress from one