earth's surface have been forming throughout untold
ages, and that successive populations differing utterly
from one another have peopled the earth in different
geological epochs. The entire point of view of thoughtful
men becomes changed in contemplating the history
of the world in which we live--albeit the newest
thought harks back to some extent to those days
when the inspired thinkers of early Greece dreamed
out the wonderful theories with which our earlier
chapters have made our readers familiar.

In the region of natural philosophy progress is no
less pronounced and no less striking. It suffices here,
however, by way of anticipation, simply to name the
greatest generalization of the century in physical
science--the doctrine of the conservation of energy.



I

THE SUCCESSORS OF NEWTON IN ASTRONOMY

HEVELIUS AND HALLEY

STRANGELY enough, the decade immediately following
Newton was one of comparative barrenness
in scientific progress, the early years of the eighteenth
century not being as productive of great astronomers
as the later years of the seventeenth, or, for