xecuted by Bessel at Konigsberg during about twelve years
previous to 1841. Wolf and Pritchard had, it is true, been beforehand
with him; but the wide scattering of the grouped stars puts the filar
micrometer at a disadvantage in measuring them, producing minute
errors which the arduous conditions of the problem render of serious
account. The heliometer, there can be no doubt, is the special
instrument for the purpose, and it was, moreover, that employed by
Bessel; so that the Konigsberg and Yale results are comparable in a
stricter sense than any others so far obtained.

One of Bessel's fifty-three stars was omitted by Dr. Elkin as too
faint for accurate determination. He added, however, seventeen stars
from the Bonn _Durchmusterung_, so that his list comprised sixty-nine,
down to 9.2 magnitude. Two independent triangulations were executed by
him in 1884-85. For the first, four stars situated near the outskirts
of the group, and marking the angles of quadrilateral by which it was
inclosed, were chosen as reference points. The second rested upon
measures of distance and position angle outward from Alcyone ([eta]
Tauri). Thus, two wholly unconnected sets of positions were secured,
the close accordance of which testified strongly to the high quality
of the entire work. They were combined, with nearly equal weights, in
the final results. A fresh reduction of the Konigsberg observations,
necessitated by recent improvements in the value of some of the
corrections employed, was the preliminary to their comparison with
those made, after an interval of forty-five years, at Yale College.
The conclusions thus laboriously arrived at are not devoid of
significance, and appear perfectly secure, so far as they go.

It has been known for some time that the stars of the Pleiades possess
a small identical proper motion. Its direction, as ascertained by
Newcomb in 1878, is about south-southeast; its amount is somewhat less
than six seconds of arc in a century. The double star 61 Cygni, in
fact, is displaced very nearly as much in one year as Alcyone with its
train in one hundred. Nor is there much probability that this slow
secular shifting is other than apparent; since it pretty accurately
reverses the course of the sun's translation through space, it may be
presumed that the _backward_ current of movement in which the Pleiades
seem to float is purely an effect of our own _onward_ traveling.

Now the curious fact emerges from Dr. Elki