them. A good telescope could distinguish between two stars
corresponding to places not more than a hundred feet apart. The
most exact measurements can determine distances ranging from
thirty to sixty feet. If a skilful astronomical observer should
mount a telescope on your premises, and determine his latitude by
observations on two or three evenings, and then you should try to
trick him by taking up the instrument and putting it at another
point one hundred feet north or south, he would find out that
something was wrong by a single night's work.

Within the past three years a wobbling of the earth's axis has
been discovered, which takes place within a circle thirty feet in
radius and sixty feet in diameter. Its effect was noticed in
astronomical observations many years ago, but the change it
produced was so small that men could not find out what the matter
was. The exact nature and amount of the wobbling is a work of the
exact astronomy of the present time.

We cannot measure across oceans from island to island. Until a
recent time we have not even measured across the continent, from
New York to San Francisco, in the most precise way. Without
astronomy we should know nothing of the distance between New York
and Liverpool, except by the time which it took steamers to run
it, a measure which would be very uncertain indeed. But by the aid
of astronomical observations and the Atlantic cables the distance
is found within a few hundred yards. Without astronomy we could
scarcely make an accurate map of the United States, except at
enormous labor and expense, and even then we could not be sure of
its correctness. But the practical astronomer being able to
determine his latitude and longitude within fifty yards, the