. The lunar period, which lies at
the foundation of the _month_, is less vitally connected with human
existence and development; but is proved by the experience of every age
and race to be eminently conducive to the progress of civilization and
culture.

But indispensable as are these heavenly measures of time to our life and
progress, and obvious as are the phenomena on which they rest, yet owing
to the circumstance that, in the economy of nature, the day, the month,
and the year are not exactly commensurable, some of the most difficult
questions in practical astronomy are those by which an accurate division
of time, applicable to the various uses of life, is derived from the
observation of the heavenly bodies. I have no doubt that, to the Supreme
Intelligence which created and rules the universe, there is a harmony
hidden to us in the numerical relation to each other of days, months,
and years; but in our ignorance of that harmony, their practical
adjustment to each other is a work of difficulty. The great
embarrassment which attended the reformation of the calendar, after the
error of the Julian period had, in the lapse of centuries, reached ten
(or rather twelve) days, sufficiently illustrates this remark. It is
most true that scientific difficulties did not form the chief obstacle.
Having been proposed under the auspices of the Roman pontiff, the
Protestant world, for a century and more, rejected the new style. It was
in various places the subject of controversy, collision, and
bloodshed.[A] It was not adopted in England till nearly two centuries
after its introduction at Rome; and in the country of Struve and the
Pulkova equatorial, they persist at the present day in adding eleven
minutes and twelve seconds to the length of the tropical year.

[Footnote A: Stern's "_Himmelskunde_," p. 72.]

GEOGRAPHICAL SCIENCE.

2. The second great practical use of an Astronomical Observatory is
connected with the science of geography. The first page of the history
of our Continent declares this truth. Profound meditation on the
sphericity of the earth was one of the main reasons which led Columbus
to undertake his momentous voyage; and his thorough acquaintance with
the astronomical science of that day was, in his own judgment, what
enabled him to overcome the almost innumerable obstacles which attended
its prosecution.[A] In return, I find that Copernicus in the very
commencement of his immortal w