ess of astronomy during the last hundred years has been rapid
and extraordinary. In its distinctive features, moreover, the nature of
that progress has been such as to lend itself with facility to
untechnical treatment. To this circumstance the present volume owes its
origin. It embodies an attempt to enable the ordinary reader to follow,
with intelligent interest, the course of modern astronomical inquiries,
and to realize (so far as it can at present be realized) the full effect
of the comprehensive change in the whole aspect, purposes, and methods
of celestial science introduced by the momentous discovery of spectrum
analysis.

Since Professor Grant's invaluable work on the _History of Physical
Astronomy_ was published, a third of a century has elapsed. During the
interval a so-called "new astronomy" has grown up by the side of the
old. One effect of its advent has been to render the science of the
heavenly bodies more popular, both in its needs and in its nature, than
formerly. More popular in its needs, since its progress now primarily
depends upon the interest in, and consequent efforts towards its
advancement of the general public; more popular in its nature, because
the kind of knowledge it now chiefly tends to accumulate is more easily
intelligible--less remote from ordinary experience--than that evolved by
the aid of the calculus from materials collected by the use of the
transit-instrument and chronograph.

It has thus become practicable to describe in simple language the most
essential parts of recent astronomical discoveries, and, being
practicable, it could not be otherwise than desirable to do so. The
service to astronomy itself would be not inconsiderable of enlisting
wider sympathies on its behalf, while to help one single mind towards a
fuller understanding of the manifold works which have in all ages
irresistibly spoken to man of the glory of God might well be an object
of no ignoble ambition.

The present volume does not profess to be a complete or exhaustive
history of astronomy during the period covered by it. Its design is to
present a view of the progress of celestial science, on its most
characteristic side, since the time of Herschel. Abstruse mathematical
theories, unless in some of their more striking results, are excluded
from consideration. These, during the eighteenth century, constituted
the sum and substance of astronomy, and their fundamental importance can
never be diminished, and s