accordingly, in the solar system, at one time void, at another 

 occupied by matter. All that has been advanced with re- 

 gard to the existence of a dark central body in the center 

 of gravity of double stars, or at least of one originally dark, 

 but faintly illuminated by the borrowed light of the planets 

 which revolve round it, belongs to the ever-enlarging realm 

 of mythical hypotheses. 



It is a more important consideration, and one more de- 

 serving of thorough investigation, that, on the supposition of 

 a revolving movement, not only of the whole of our planet- 

 ary system which changes its place, but also for the proper 

 motion of the fixed ^stars at their various distances, the cen- 

 ter of this revolving motion must be 90 distant* from the 

 point toward which our solar system is moving. In this con- 

 nection of ideas, the position of stars possessing a great or 

 very small proper motion becomes of considerable moment. 

 Argelander has examined, with his usual caution and acute- 

 ness, the degree of probability with which we may seek for 

 a general center of attraction for our starry stratum in the 

 constellation of Perseus. t Madler, rejecting the hypothesis 

 of the existence of a central body preponderating in mass, 

 as the universal center of gravity, seeks the center of grav- 

 ity in the Pleiades, in the very center of this group, in or 

 nearf to the bright star TJ Tauri (Alcyone). The present is 



* Argelander, ibid., p. 42 ; Madler, CentraJsonne, s. 9, and Astr., s. 

 403. 



t Argelauder, ibid., p. 43 ; and in Sebum., Astr. Nachr., No. 566. 

 Guided by no numerical investigations, but following the suggestions of 

 fancy, Kant long ago fixed upon Sirius, and Lambert upon the nebula 

 in the belt of Orion, as the central body of our starry stratum. (Struve, 

 Astr. Stell., p. 17, No. 19.) 



t Madler, Astr., s. 380, 400, 407, and 414 ; in his Centraltonne, 1846, 

 p. 44-47 ; in Untersiickungen uber die Fixstern-Systeme, th. ii., s. 183- 

 185. Alcyone is in R. A. 54 30', Decl. 23 36', for the year 1840. If 

 Alcyone's parallax were really 0"-0065, its distance would be equal to 

 3H million semi-diameters of the earth's orbit, and thus it would be 

 fifty times further distant from us than the distance of the double star 

 61 Cygni, according to Bessel's earliest calculation. The light which 

 comes to the earth from the sun in 8' 18"-2, would in that case take 500 

 years to pass from Alcyone to the earth. The fancy of the Greeks de- 

 lighted itself in wild visions of the height of falls. In Hesiod's Theo- 

 gonia, v. 722-725, it is said, speaking of the fall of the Titans into Tar- 

 tarus: " If a brazen anvil were to fall from heaven nine days and nine 

 nights long, it would reach the earth on the tenth." This descent of 

 the anvil in 777,600 seconds of time gives an equivalent in distance of 

 309,424 geographical miles (allowance being made, according to Galle's 

 calculation, for the considerable diminution in the force of attraction at 

 planetary distances), therefore 1 i times the distance of the moon from 



