in proportion to their actual size and the distance at which they are
placed from us. Attempts have been made to ascertain the distance of
some of the stars by calculations founded on parallax, it being
previously understood that, if a parallax of so much as one second,
or the 3600th of a degree, could be ascertained in any one instance,
the distance might be assumed in that instance as not less than
19,200 millions of miles! In the case of the most brilliant star,
Sirius, even this minute parallax could not be found; from which of
course it was to be inferred that the distance of that star is
something beyond the vast distance which has been stated. In some
others, on which the experiment has been tried, no sensible parallax
could be detected; from which the same inference was to be made in
their case. But a sensible parallax of about one second has been
ascertained in the case of the double star, alpha alpha, of the
constellation of the Centaur, {3} and one of the third of that amount
for the double star, 61 Cygni; which gave reason to presume that the
distance of the former might be about twenty thousand millions of
miles, and the latter of much greater amount. If we suppose that
similar intervals exist between all the stars, we shall readily see
that the space occupied by even the comparatively small number
visible to the naked eye, must be vast beyond all powers of
conception.

The number visible to the eye is about three thousand; but when a
telescope of small power is directed to the heavens, a great number
more come into view, and the number is ever increased in proportion
to the increased power of the instrument. In one place, where they
are more thickly sown than elsewhere, Sir William Herschel reckoned
that fifty thousand passed over a field of view two degrees in
breadth in a single hour. It was first surmised by the ancient