AN ACCOUNT OF THE ASTRONOMICAL OBSERVATORY AT COR- 

 DOBA, ARGENTINE REPUBLIC. 



An address to citizens of Boston hy Dr. B. A. Gould, the Director. 



More tlian half a century ago the great astronomer Bessel undertook 

 the formation of a catalogue which should contain the positions and 

 magnitudes of as many stars as possible between the parallels of 45° 

 north decliuation and 15° south, down to the ninth magnitude; thus 

 including all stars one-fifteenth part as bright as the faintest which 

 he could discern with the naked eye. This great work he carried to a 

 successful conclusion ; commencing the observations in 1821 and com- 

 pleting them in 1833, and securing more than 72,000 observations of 

 62,380 different stars. These have since been carefully computed, and 

 the resultant catalogues published by the Imperial Observatory of 

 Russia, at the jmblic expense, affording a priceless aid to astronomers. 

 In France an analogous attempt had been made near the close of the 

 last century, by La Lande, who undertook a scrutiny of all the stars 

 between the north pole and the southern tropic, and his 47,000 observa- 

 tions have been computed and published at the expense of the British 

 government; but the superiority of modern instruments and methods 

 rendered Bessel's undertaking essentially a new one. 



Later, his pupil and assistant, Argelander, upon whom his mantle 

 had fallen, extended his scrutiny by two more series of zone-observa- 

 tions — one on the north, reaching from 45° to 80°, the other on the south 

 from 15"^ to 31°, the two jointly containing about 50,000 observations. 

 The vicinity to the pole upon the one side and to the horizon on the other, 

 presented peculiar difficulties, yet the continued improvement of astro- 

 nomical instruments and methods, and the rare skill of Argelander, 

 enabled him to attain both a somewhat higher degree of accuracy and 

 a relatively greater number of observations. Thus, in 1852, the 

 heavens had been well studied from 80*^ north of the equator to 31° 

 south; and when in that year our lamented countryman, Gilliss, re- 

 turned from his expedition to Chile, he brought with him the manuscript 

 results of an extensive series of zones, which he had observed around 

 the south pole. Soon afterward, the English astronomer, Carrington, 

 explored the ten degrees around the north pole; so that for the last 

 eighteen years the only region of the heavens which has not been care- 

 fully investigated is that which lies between the parallel of 31° south 

 and the northern limit of Gilliss's yet unpublished observations. To 

 fill this hiatus and complete the survey of the heavens on some plan 



