[ 237 ] 120 



tion, from a base of about two miles in length, has been spread over the 

 lower delta. The latitude of a point designated as the astronomical sta- 

 tion, has been determined by 157 observations upon 22 fixed stars selected 

 for the purpose. The difference of zenith distance of those stars, by pairs, 

 was measured directly by a spider-line micrometer, applied to a 42 inch 

 altitude and azimuth telescupe, niade by Troughton and Simms. In addi- 

 tion, a series of observations was made for determining the longitude, by 

 Observing the transit of the moon, and such stars as are given in the Nauti- 

 cal Almanac under the head of nioo?i cul/mnatin^c sta7's ; and such other 

 observations on high and low stars as would furnish data for correcting all in- 

 strumental errors. 



The position of the astronomical station on Balize bayou, Northeast Pass, 

 is concluded to be in latitude 29^ 7' 4".59 north, longitude 89° 4' 32".57 

 west of Greenwich. 



From this point. Captain Talcott has deduced the positions of all the im- 

 portant points embraced in his survey; and it is from the unpublished ac- 

 count of his valuable work that 1 have been allowed to select the results 

 for the main passes of the mouth of the Mississippi, which are introduced 

 in the Table of Geographical Positions. 



XVIII. NEW ORLEANS — THE ROMAN CATHOLIC CATHEDRAL. 



The longitude of this place has been variously staled in the course of 

 the past half century. In the Connaissance des Terns from 1793 to 1829, 

 inclusive, it is given, under the authority of the French academicians, at oh. 

 59w. 53.5s. west of Greenwich. 



In England, the useful Requisite Tables make it to be 5A. 59m. 55*. 



Don Jose Joachim de Ferrer, in his valuable list of geographical posi- 

 tions, published in the Connaissance des Terns for 1817, increases this lon- 

 gitude to 6/i. Qm. 2\s. 



Since that period, this last longitude has superseded the first two above 

 quoted, with the exception that some slight changes have been introduced, 

 from time to time, by different aiuhorities ; such as the Connaissance des 

 Terns from 1830 to 1843, inclusive, and the American Almanac for the same 

 period. In theabsenceof the data upon which these various results have been 

 founded, it would be ditficult for me even to have an opinion as to which 

 should be adopted, were it not that the work of Captain Talcott, spoken of 

 in the last article, affords me, in connexiou with what I had before myself 

 the means of offering, some new data for the discussion of this interesting 

 question. 



In the latter part of May, 1835. I spent three days at the Pilot house on 

 the east bayou of the Southwest Pass. I made the latitude of that place 

 = 29° 59' 34", and the difference of longitude east of the Cathedral of New 

 Orleans = 2m,. 4.5s. 



Taking the absolute longitude of the same station as determined by Cap- 

 tain Talcott, and combining it with my observed difference, we have longi- 

 tude of New Orleans Cathedral (5h. ()/«. Is. 



In January, 1840, Major J. D. Graham, of the United States topograph- 

 ical engineers, on his way to the Sabine river, to survey the boundary 

 between the United States and Texas, observed the difference of longi- 

 tude between New Orleans and one of Captain Talcott's stations — the new 

 Southwest Pass light-house. He was supplied with three chronometers j 



