ASTRONOMY FOR 1889, 1890. 125 



logues of Weisse appeared iu 1846 and 1863. From J 841 to 1852 Arge- 

 lander coutinued his work at Bonu, and his northern zones (published in 

 1846) contain 22,000 stars between +45^ and +800 and the southern 

 zones (published in 1852) 17,000 between — 15c> and — 31°, catalogued 

 by Oeltzen (1851 to 1857). The positions in these different catalogues 

 depend upon meridian observations. 



In 1852, having finished his zones, Argelander conceived the plan of a 

 work of much greater extent. It was to fix approximately the positions 

 of all stars to the ninth magnitude, and perhaps a little below (9.5), visi- 

 ble in our latitudes. To accomplish this the plan was to employ simply a 

 small telescope, the observer, with his eye always at the telescope, to call 

 out to a recorder, who sat close by with a chronometer. The preliminary 

 trials, by J. Schmidt, being successful, the work wa.s begun, and, with 

 the help of Kruegerand Schoenfeld, on whom the greater part of the la- 

 bor fell, the revision of the northern sky was finished in 1859 ; and this 

 is the work that we know as the "Bonn Durchmusterung." 



TheDurchmusterung,published between 1859 and 1862 in volumes 3, 4, 

 and 5 of the Bonn Observations, contains no less than 324,198 stars, lying 

 between 2P south declination and the north pole, the zone between +81<^ 

 and the pole being a revision of Carrington's catalogue. Volume 6 of 

 the "Bonn Beobachtungen," contains futhermore 34,000 positions, deter- 

 mined by Argelander with the meridian circle. The stars of the 

 Durchmusteruug are plotted on a series of charts published in 1863. 

 Since Argelander's death Schoenfeld has completed a similar piece of 

 work for our southern sky, the " Siidliche Durchmusteruug " (1886), con- 

 taining more than 133,000 stars, between — 2° and— 23°, and Gould at 

 Cordoba has extended the zones to the neighborhood of the south pole. 



Upon the organization of the International Astronomische Gesell- 

 schaft in 1865, the question at once came up of undertaking, by the co-op- 

 eration of several observatories, the exact determination of the positions 

 of all these stars provisionally catalogued in the Durchmusteruug. A 

 programme for the work, prepared by a special committee, was.finally 

 decided upon at the meeting in Vienna in 1869. The new revision was 

 confined to the limits of —2° and +80° declination, the positions of 

 the circumpolars seeming to be sufficiently well known from the work 

 of Carrington and that of the astronomers at Hamburg and Kazan. The 

 zones were at first assigned as follows : 



Pulkowa undertook the determination of 539 fundamental stars care- 

 fully selected by Dr. Auwers, which should form points of reference. 

 In the 20 years that have elapsed since the great catalogue was 



