lled among
other intelligent beings elsewhere who can see it. I can only adopt
the title of "Earth," and therefore I add this line. Now our address
is so complete that from anywhere in the solar system--from Mercury,
from Jupiter, or Neptune--there ought to be no mistake about the
letter finding its way to Mr. John Smith. But from his correspondent
in the Great Bear this address would be still incomplete; they cannot
see our earth from there, and even the sun himself only looks like a
small star--like one, in fact, of thousands of stars elsewhere.
However, each star can be distinguished, and our sun may, for
instance, be recognized from the Great Bear by some designation. We
shall add the line "Near the Sun," and then I think that from this
constellation, or from any of the other stars around us, the address
of Mr. John Smith may be regarded as complete. But Mr. Smith's
correspondence may be still wider. He may have an agent living in the
cluster of Perseus or on some other objects still fainter and more
distant; then "Near the Sun" is utterly inadequate as a concluding
line to the address, for the sun, if it can be seen at all from
thence, will be only of the significance of an excessively minute
star, no more to be designated by a special name than are each of the
several leaves on the trees of a forest. What this distant
correspondent will be acquainted with is not the earth or the sun but
only the cluster of stars among which the sun is but a unit. Again we
use our own name to denote the cluster, and we call it the "Milky
Way." When we add this line, we have made the address of Mr. John
Smith as complete as circumstances will permit. I think a letter
posted to him anywhere ought to reach its destination. To perfect it,
however, we will finish up with one line more--"The Universe."

The Distances of the Stars.

I must now tell you something about the distances of the stars. I
shall not make the attempt to explain fully how astronomers make such
measurements, but I will give you some notion of how it is done. You
may remember I showed you how we found the distance of a globe that
was hung from the ceiling. The principle of the method for finding the
distance of a star is somewhat similar, except that we make the two
observations not from the two ends of a table, not even from opposite
sides of the earth, but from two opposite points on the earth's orbit,
which are therefore at a distance of one hundred and eighty-