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seem to belong to a group of nearly uniform
magnitude have the same proper motion.
The spectroscope has shown that these have
also often the same velocity in the line of
ˆ ˆ ˆ ˆ
sight. Thus in the Great Bear, I, I, I, I,
ˆ ˆ
I, all agree as to angular proper motion. I
was too faint for a spectroscopic measure-
ment, but all the others have been shown
to be approaching us at a rate of twelve to
587