ASTRONOMY FOR 1889, 1890. 125 



logues of Weisse appeared in 1840 and 18C3. From J 841 to 18515 Arge- 

 lauder continued his work at Bonn, and bis northern zones (published in 

 1S4G) contain 22,000 stars between +45^ and +80^ and tlie southern 

 zones (published in 1852) 17,000 between —island —31°, catalogued 

 b^^ Oeltzen (1851 to 1857). The positions in these ditterent 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 was begun, and, with 

 the help of Krueger and 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 Dnrchmusterung." 



TheDurchmusterung,published between 1859 and 1802 in volumes 3, 4, 

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

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

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

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

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

 Dnrchmusterung 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 " Slidliche Dnrchmusterung" (1880), 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- 

 schaftin 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 Dnrchmusterung. A 

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

 decided u[)on at the meeting in Vienna in 1869. The new revision was 

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

 the circumpolars seeming to be sufficiently well known from the work 

 of Carringtou and that of the astronomers at Hamburg and Kazan, The 

 zones were at first assianed as follows : 



jland). 



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 



