272 OBSERVATORY AT CORDOBA, ARGENTINE REPUBLIC. 



nitude inclusive, and no others, and accompanied by the corresponding 

 catalogues. As a matter of simple justice and proj)riety, I have given 

 it the name of Uranometria Argentina. The magnitude of each star 

 has been determined on the average by more than four observations, 

 and by as many as three different observers. At present, Mr. Thome, 

 whom I have left in charge of the observatory, and who is the only one 

 of the original corps now remaining in Cordoba, is engaged in a last 

 syst'Omatic scrutiny of the finished work, to insure that no star is either 

 omitted or wfongly placed. Much more than a quarter part of the 

 actual observation has been done by him ; and from his constant and 

 assiduous devotion to the undertaking for nearly four years, I am sure 

 that he now possesses a greater personal familiarity with the southern- 

 sky than any man ever attained before. Nor does this comparison iu 

 the least diminish the honor due to his late colleagues, to whom a laige 

 portion of the excellence of the work must justly be attributed. Of 

 another assistant, not on the observatory's books, but without whose 

 untiring and devoted aid my work could scarcely have been accom- 

 plished, I may not speak. 



Less than two years ago there was published by Professor Heis a 

 new uranometry of the northern sky, precisely on the same plan as 

 Argelander's, of which it is, in fact, an enlargement, with the addition 

 of fainter stars seen with his unassisted eye, which is of exceptional 

 strength. My plan was somewhat ditferent, and we availed ourselves 

 of opera-glasses to obtain more accurate estimates; and after I found 

 the stars of the seventh magnitude as distinctly visible at Cordoba to 

 eyes of average power, I fixed this magnitude as the limit for the uran- 

 ometry, a large number of fainter stars being excluded, although their 

 magnitudes have been well determined. If we only consider stars as 

 bright as the sixth magnitude, Heis found 3,139 of these in the northern 

 half of the sky, while we have only three-quarters as many in the southern 

 half. Yet while he has in all 4,909 northern stars, we have 7,670 southern 

 ones, so great is the difference between the transparency of the sky at Cor- 

 doba and at Miinster. The number of stars in the whole sky visible to the 

 naked eye has usually been estimated at about 5,500. Heis estimates 

 that there are about 6,800 of a brightness not inferior to the faintest 

 which he can see. But I now find that if the sky was as transparent 

 as that at Cordoba on a good night, even an average eye would probably 

 discern not much less than 15,000 in the full circuit of the heavens. 

 The Uranometria Argentina contains 8,522 stars, of which 7,670 are 

 situated in the southern heavens, and 852, or just one-tenth of the 

 whole, ate within the first ten degrees of north declination. 



In connection with the uranometry, an opportunity presented itself 

 to introduce, or rather to suggest to astronomers for their acceptance, a 

 greatly-needed reform in the arrangement and boundaries of the south- 

 ern constellations, which have from the beginning been in a state of 

 such confusion as to call forth continual complaints from those who 



