that known line, we can mark the
inclination of those telescopes to each other when focussed upon a
particular mountain peak on the moon; by this means we know the angle
of parallax (180 deg. less the sum of the two angles of inclination), and,
from this and our known length of base line, we can calculate the
distance. When however we go a step further and attempt to calculate
the distance of the Sun (93,000,000 miles), we find our last base line
again absolutely inadequate. But the astronomer helps us again; we now
separate our two telescopic eyes by the whole diameter of the earth
(7900 miles); this is accomplished by taking from the Equator two
simultaneous observations of the Sun, at its rising and setting; for
when the Sun is setting, at say the Equinox, it is at that moment
rising at exactly the other side of the earth; the inclination of the
two telescopes, directed to a certain point on the Sun, will now give
the distance approximately, though even this base line is too short
for exactitude. When however we attempt to go still further and try to
ascertain the distance of stars, which are a million times further off
than the Sun, such a base line is quite out of the question. How then
can we get a base line for our telescopes longer than the whole width
of the earth? The Astronomer again provides the means. The earth takes
one year to complete its vast orbit round the sun, and the diameter of
that path is 186,000,000 miles. This is made our new base line for
separating our telescopes; an observation of a star is taken, say,
to-day, and after waiting six months, to enable the earth to reach the
other extremity of its vast orbit, another observation is taken, and
yet it is found, as we shall see later on, that the distance of the
nearest fixed star is so _stupendous_ that even this base line, of
186,000,000 miles, shows absolutely no inclination between the two
telescopes except in about a dozen cases, and even in those the angle
of parallax, perceivable, is so minute that no reliable distance can
be calculated; we can only say that the star is at least as far away
as a certain distance, but it may be much farther.

Let us now try by other means to get a clearer insight into the
subject of this View, by tracing Space to the utmost limit of human
conception. I think the best method I can adopt will be to take you,
in imagination, for a journey as far as is possible by means of the
best instruments at our disposal.