a distinct conception of infinity, but, for that matter, it
cannot be said that any one to-day has a conception of infinity
that could be called definite. But, reasoning from experience and
the reports of travellers, there was nothing to suggest to early
man the limit of the earth. He did, indeed, find in his
wanderings, that changed climatic conditions barred him from
farther progress; but beyond the farthest reaches of his
migrations, the seemingly flat land-surfaces and water-surfaces
stretched away unbroken and, to all appearances, without end. It
would require a reach of the philosophical imagination to
conceive a limit to the earth, and while such imaginings may have
been current in the prehistoric period, we can have no proof of
them, and we may well postpone consideration of man's early
dreamings as to the shape of the earth until we enter the
historical epoch where we stand on firm ground.

2. Primitive man must, from a very early period, have observed
that the sun gives heat and light, and that the moon and stars
seem to give light only and no heat. It required but a slight
extension of this observation to note that the changing phases of
the seasons were associated with the seeming approach and
recession of the sun. This observation, however, could not have
been made until man had migrated from the tropical regions, and
had reached a stage of mechanical development enabling him to
live in subtropical or temperate zones. Even then it is
conceivable that a long period must have elapsed before a direct
causal relation was felt to exist between the shifting of the sun
and the shifting of the seasons; because, as every one knows, the
periods of greatest heat in summer and greatest cold in winter
usually come some weeks after the time of the solstices. Yet, the