SKETCH OF FRIED RICH W. A. ARGELANDER. 55 i 



land was also his wedding tour ; and he went "by way of Dorpat, 

 where he renewed his friendship with Struve, and St. Petersburg. 

 The observatory at Abo, newly built, was not yet fully furnished, 

 and the nature of the observations was considerably determined 

 by the consideration of the instruments that were available. The 

 earlier ones were upon comets, and those made with the meridian 

 circle ; and Argelander computed the orbit of the comet of 1718 

 from Kirch's observations. 



Attention was next given to the proper motions of the stars, 

 the study of which, although touched upon by Bradley and 

 resumed by Piazzi, was still in its beginning. At this time the 

 Konigsberg Observatory was extending the knowledge of the 

 stars in mass ; Dorpat, that of double stars ; and Greenwich, that 

 of stars visible to the naked eye ; and Argelander devoted his ob- 

 servatory to the stars the yearly motion of which was given by 

 Bradley and Piazzi as 0'2" or more, as well as of those of which 

 were suspected of having motions. These stars were to be ob- 

 served at least four times a year, in every position of the circle. 



The observations made at Abo were published down to 1828, 

 in three volumes, while the rest were still awaiting publication 

 at the time of Argelander's death. The steps taken to insure the 

 highest accuracy are fully set forth in the introduction to the 

 second volume. The catalogue at once took a first place among 

 the records which gave the fundamental determinations of the 

 star places for 1830. It is also a model for convenience. 



The buildings, collections, and library of the university hav- 

 ing been destroyed by the great fire which visited Abo in Septem- 

 ber, 1827, although the observatory was saved, it was determined 

 to remove the whole concern to Helsingfors. Argelander was 

 appointed a Professor in Ordinary of Astronomy in the new uni- 

 versity, but did not remove from Abo till 1831. Then, having 

 visited his old home after eight years of absence and renewed his 

 association with Bessel, he settled in Helsingfors in August, 1832, 

 while the buildings were still in a backward condition, so that he 

 was not able to make an observation for nearly a year, and all 

 was not complete till September, 1835. To the Helsingfors period 

 belong observations of the brighter circumpolar stars, of the 

 bending of the meridian circle, and the printing of the Abo cata- 

 logue ; and the celebrated treatise on the proper motion of the 

 solar system. Supported by the results obtained at Abo, he found 

 that the regularity of the stellar motions, which is explained by a 

 movement of the sun toward the constellation Hercules, first ten- 

 tatively announced by Herschel, was borne out by the observa- 

 tions. 



In August, 1836, Argelander was invited to remove to the still 

 young University of Bonn, where the Prussian Government had 



