Note 9 — Chapter II

“Here then we have the splendid result of the united studies of MM. Argelander, O. Struve, and Peters, grounded on observations made at the three observatories of Dorpat, Abo, Pulkova, and which is expressed in the following thesis:—The motion of the solar system in space is directed to a point of the celestial vault situated on the right line which joins the two stars π and μ Herculis, at a quarter of the apparent distance of these stars, reckoning from π Herculis. The velocity of this motion is such, that the sun, with all the bodies which depend upon it, advances annually in the above direction 1·623 times the radius of the earth’s orbit, or 33,550,000 geographical miles. The possible error of this last number amounts to 1,733,000 geographical miles, or to a seventh of the whole value. We may then wager 400,000 to 1 that the sun has a proper progressive motion, and 1 to 1 that it is comprised between the limits of thirty-eight and twenty-nine millions of geographical miles.”—Etudes d’Astronomie Stellaire: Sur la Voie Lactée et sur les Distances des Etoiles Fixes: M. F. W. G. Struve. [A report addressed to his Excellency M. Le Comte Ouvaroff; Minister of Public Instruction and President of the Imperial Academy of Sciences at St. Petersburg.]