visible to the unaided eve. And the more carefully
the motions of the stars are studied, the more evident
it becomes that widely separated stars are linked together
into infinitely complex systems, as yet but little
understood. At the same time, all instrumental advances
tend to resolve more and more seemingly single
stars into close pairs and minor clusters. The two
Herschels between them discovered some thousands
of these close multiple systems; Struve and others increased
the list to above ten thousand; and Mr. S. W.
Burnham, of late years the most enthusiastic and successful
of double-star pursuers, added a thousand new
discoveries while he was still an amateur in astronomy,
and by profession the stenographer of a Chicago court.
Clearly the actual number of multiple stars is beyond
all present estimate.

The elder Herschel's early studies of double stars
were undertaken in the hope that these objects might
aid him in ascertaining the actual distance of a star,
through measurement of its annual parallax--that is to
say, of the angle which the diameter of the earth's
orbit would subtend as seen from the star. The expectation
was not fulfilled. The apparent shift of
position of a star as viewed from opposite sides of the
earth's orbit, from which the parallax might be estimated,
is so extremely minute that it proved utterly
inappreciable, even to the almost preternaturally acute
vision of Herschel, with the aid of any instrumental
means then at command. So the problem of star distance