554 THE POPULAR SCIENCE MONTHLY. 



between the north pole and two degrees of south declination. 

 Leaving the execution of these observations to his assistants, Ar- 

 gelander started with Struve, in June, 1852, by way of Gottingen 

 and Berlin, to Sweden and Finland, and thence to Pultova, where 

 he spent four weeks, to return at the end of September with the 

 best impressions and in full vigor. The winter and spring of 1854 

 were so favorable to observations, while the reduction-tables were 

 not far behind them, that Argelander could rejoice in the thought 

 that the atlas would contain from fifty to a hundred thousand 

 more stars than he had originally contemplated. Ever careful to 

 preserve the unity of the whole, he arranged most of the materials 

 himself, and was not willing to let a zone pass without personally 

 working upon it. Double stars and stars with greater proper mo- 

 tions were noted; Winnecke's and Kruger's determinations of 

 parallax were connected with these, and the restoration of lost 

 stars from the older observations afforded ever-new interest. The 

 revisions went on till the summer of 1861 ; but in some of the re- 

 gions they no longer required all of Argelander's time, and he was 

 able to pursue other objects. He identified all the stars of the 

 eighth magnitude and brighter, which were not found in the earlier 

 catalogues, with the accessible variable stars, the stars for com- 

 parison with the Mannheim observations of nebulae and for former 

 appearances of periodical comets, and especially many stars with 

 presumed or determined proper motions. Next, while still occu- 

 pied with the collation of his material, Argelander turned his eye 

 to a work he had long contemplated, of more exact meridian ob- 

 servations of all the stars to the ninth magnitude, of which the 

 Durchmusterung had made known the general positions. The 

 labor, too much for a single establishment, was to be divided 

 among different observatories. So, in the summer of 18G5, he 

 made a proposition for the simultaneous observation of selected 

 stars at different points, by which he hoped to obtain material for 

 the investigation of star catalogues in general, and to secure the 

 needed number of fixed points for the greater work. The plan 

 for this work was first presented, in 1867, to the officers of the 

 University at Bonn, and afterward at the general meeting of the 

 Astronomische Gesellschaft, where the author also gave his views 

 respecting the most convenient way of carrying it out. With 

 some slight modifications they form the basis of the programme 

 decided upon by the society at Vienna in 1869. 



Argelander undertook a small part of the preliminary work 

 for the execution of this scheme, but found that, at the age of 

 seventy years, he was no longer competent to make the necessary 

 observations, and he gave them over to his assistants, carrying on 

 himself only the minor series. The main part of the treatise on 

 the subject was printed only a short time before his death. 



