124 ASTRONOMY FOR 1889, 1860. 



Precession. — A useful table of the third term of the precession has 

 been computed by Herr Kloock and published by the Kiel Observatory. 



Earliiess^s astronomical, physical, and geodetic constants. — Prof. Wm. 

 Harkness, of the U. S. Naval Observatory, has been at work for some 

 time upon a homogeneous system of inter-related constants, more 

 trustworthy values of which are to be attained by the solution of equa- 

 tions of condition, in which the best values resulting from observation 

 are introduced and combined with the expression of their mutual re- 

 lations. 



A preliminary communication of results was made to the Astronom- 

 ical Journal, No. 194, but it seems preferable to quote here the final 

 values published by Professor Harkness in Appendix III to the Wash- 

 ington Observations for 1891, though the latter work was not issued 

 till after the close of the year 1890. 



Professor Harkness has collected the various determinations of each 

 of the constants in question, decided upon the values to be adopted in 

 the computations, often using the method of least squares for this pur- 

 pose; and has then employed this method in order to obtain a resultant 

 homogeneous system. 



Among the results obtained are the following : 



Earth's equatorial semi-diaraeter 6,377 972 ± 1 248 meters. 



Earth's polar semi-diameter ,6,356 727 -[-99.1 meters. 



Length of seconds-pendulum 0°'.990 91 + 0™.005 29 sin V- 



Length of sidereal day 86 164.099 65 mean solar seconds. 



Length of sidereal year 365<> 6^ 9"^ 9\314. 



Solar parallax 8".809 05±0".005 67. 



Lunar parallax. 3 422"..542 16 ±0".125 33. 



Constant of aberration 20". 454 51 ± 0".012 58. 



The mean distance of the earth from the sun, with the above value 

 of the solar parallax is 92,79G 9;j0±59 715 miles, or 149,3'40 870±9G 101 

 kilometers. 



STAR CATALOGUES. 



The star catalogue of the Astronomische GeseUschaft. — The first parts 

 of the great catalogue of the Astronomische GeseUschaft ajjpeared in 

 1890. They are the volumes coutaiuiug the catalogues of zones ob- 

 served by Krueger at Helsiugfors and Gotha, by Boss, at Albany, and 

 by Fearnley and Geelmuyden at Christiania. The two first mentioned 

 volumes contain respectively the positions of 14,680 and of 8,241 stars 

 for the equinox of 1875. 



It may be worth while to recall here the origin of this great under- 

 taking, now nearing completion. The zones of the Histoire celeste 

 frangaise, published by Lalande comprise about 50,000 stars from 

 the first to the eighth magnitude, but they were not catalogued till 

 nearly half a century after their completion. Those of Bessel, observed 

 at Koenigsberg from 1821 to 1833, contain 62,600 stars from the first to 

 the ninth magnitude between —15° and + 45° declination; the two cata- 



