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.
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