Now the curious fact emerges from Dr. Elkin’s inquiries that six of Bessel’s stars are exempt from the general drift of the group.  They are being progressively left behind.  The inference is obvious that they do not in reality belong to, but are merely accidentally projected upon, it; or, rather, that it is projected upon them; for their apparent immobility (which, in two of the six, may be called absolute) shows them with tolerable certainty to be indefinitely more remote—­so remote that the path, moderately estimated at 21,000,000,000 miles in length, traversed by the solar system during the forty-five years elapsed since the Konigsberg measures dwindles into visual insensibility when beheld from them.  The brightest of these six far-off stars is just above the eighth (7.9) magnitude; the others range from 8.5 down to below the ninth.

A chart of the relative displacements indicated for Bessel’s stars by the differences in their inter-mutual positions as determined at Konigsberg and Yale accompanies the paper before us.  Divergences exceeding 0.40” (taken as the limit of probable error) are regarded as due to real motion; and this is the case with twenty-six stars besides the half dozen already mentioned as destined deserters from the group.  With these last may be associated two stars surmised, for an opposite reason, to stand aloof from it.  Instead of tarrying behind, they are hurrying on in front.

An excess of the proper movement of their companions belongs to them; and since that movement is presumably an effect of secular parallax, we are justified in inferring their possession of an extra share of it to signify their greater proximity to the sun.  Hence, of all the stars in the Pleiades these are the most likely to have a measurable annual parallax.  One is a star a little above the seventh magnitude, distinguished as s Pleiadum; the other, of about the eighth, is numbered 25 in Bessel’s list.  Dr. Elkin has not omitted to remark that the conjecture of their disconnection from the cluster is confirmed by the circumstance that its typical spectrum (as shown on Prof.  Pickering’s plates) is varied in s by the marked character of the K line.  The spectrum of its fellow traveler (No. 25) is still undetermined.

It is improbable, however, that even these nearer stars are practicable subjects for the direct determination of annual parallax.  By indirect means, however, we can obtain some idea of their distance.  All that we want to know for the purpose is the rate of the sun’s motion; its direction we may consider as given with approximate accuracy by Airy’s investigation.  Now, spectroscopic measurements of stellar movements of approach and recession will eventually afford ample materials from which to deduce the solar, velocity; though they are as yet not accurate or numerous enough to found any definitive conclusion upon.  Nevertheless, M. Homann’s preliminary result of fifteen miles