ngated at Pulkowa. In a few years
they became easily separable once more. If the
one-hundred-and-seventy-year period is correct, they should continue to
get farther apart until about 1921. According to Asaph Hall, their
greatest apparent distance is 6.3", and their least apparent distance
0.5"; consequently, they will never again close up beyond the separating
power of existing telescopes.

There is a great charm in watching this pair of stars even with a
three-inch telescope--not so much on account of what is seen, although
they are very beautiful, as on account of what we know they are doing.
It is no slight thing to behold two distant stars obeying the law that
makes a stone fall to the ground and compels the earth to swing round
the sun.

In theta we discover a fine triple, magnitudes four and a half, nine,
and ten; distances 7", p. 345 deg., and 65", p. 295 deg.. The ninth-magnitude
star has been described as "violet," but such designations of color are
often misleading when the star is very faint. On the other hand it
should not be assumed that a certain color does not exist because the
observer can not perceive it, for experience shows that there is a wide
difference among observers in the power of the eye to distinguish color.
I have known persons who could not perceive the difference of hue in
some of the most beautifully contrasted colored doubles to be found in
the sky. I am acquainted with an astronomer of long experience in the
use of telescopes, whose eye is so deficient in color sense that he
denies that there are any decided colors among the stars. Such persons
miss one of the finest pleasures of the telescope. In examining theta
Virginis we shall do best to use our largest aperture, viz., the
five-inch. Yet Webb records that all three of the stars in this triple
have been seen with a telescope of only three inches aperture. The
amateur must remember in such cases how much depends upon practice as
well as upon the condition of the atmosphere. There are lamentably few
nights in a year when even the best telescope is ideally perfect in
performance, but every night's observation increases the capacity of the
eye, begetting a kind of critical judgment which renders it to some
extent independent of atmospheric vagaries. It will also be found that
the idiosyncrasies of the observer are reflected in his instrument,
which seems to have its fits of excellence, its inspirations so to
speak, while at other times