OBSERVATOEY AT CORDOBA, ARGENTINE REPUBLIC. 271 



generation will probably pass before they disappear. Thus season after 

 season passed away, and it was not till May, 1873, that the meridian- 

 circle was mounted ready for use, nor until the 9th of September, 1872, 

 that the regular observations were commenced for the celestial survey 

 which I had planned seven years before. 



But this long delay proved in the end not to have been a misfortune, 

 irksome as it was. Within the first mouth it became evident that the 

 construction of the building would demand a disproportionate amount 

 of time and attention, and that although the large telescope might be 

 employed to some extent, a long time must elapse before the work with 

 the meridian-circle could begin. Although I little dreamed how great 

 would be the delay, I determined to use this opportunity for the con- 

 struction of a uranometry, or catalogue of all the visible stars of the 

 southern sky, with an exact determination of the brilliancy of each. 

 The labor of these first eighteen months was certainly as assiduous and 

 fruitful, and I believe it was as serviceable to science, as the later work. 

 Thirty years before, Argelander had made such a uranometry, giving 

 tiie brightness of each star to the nearest third of a unit of magnitude. 

 In Albany, in 1858, we had done the same work, for a portion of the 

 heavens, to tenths of a magnitude, while awaiting the mounting of the 

 instruments. These observations, although stereotyped at the time, 

 have never been published ; but they had given me a good deal of expe- 

 rience, which now became very useful. 



Thus the scientific labors of the first year went to the construction of 

 star-lists and charts of the visible heavens, as they appeared on the 

 clearest nights to the sharpest unassisted eyes, the magnitudes being 

 estimated to tenths of a unit. Ifo instruments were used other than 

 common opera glasses ; but the purity of the air at Cordoba, and an ele- 

 vation of about 1,300 feet above the sea-level, give a remarkable trans- 

 parency to the atmosphere on favorable nights. My own near-sighted- 

 ness precluded me from taking part in the actual observations, but I 

 found more than enough to do in identifying those stars whose places had 

 been determined by previous astronomers, in providing for our own 

 future observation of those not to be found in the catalogues, in main- 

 taining a uniform system of estimates by the four observers, and in the 

 general management of the work. Every test in my power was brought 

 to bear upon the accuracy of the work as it progressed, and each scrutiny 

 served to confirm my confidence in the carefulness of all engaged in 

 the observations. After the completion of this undertaking, the results 

 were subjected to careful revision by repeating the whole process in a 

 somewhat different form, assigning to each of the observers a region 

 which in the first scrutiny had been given to some other one. The defi- 

 nite results are now available for publication, and the Argentine govern- 

 ment has authorized me to make the necessary arrangements. The 

 published work will consist of an atlas of the heavens, from 10° north 

 of the equator to the south pole, showing every star to the seventh mag- 



