[ 237 3                           12Q
tion, from a base of about two miles in length, has been spread1 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 telescope, made by Troughton and Simms. In addi-
tion, a series of observations was made for determining the longitude, by
dbserving the transit of the moon, and such stars as are given in the Nauti-
cal Almanac under the head of moon culminating stars ; 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° V 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portant points embraced in his survey; and it is from the unpublished ac-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 I 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 stated in the course of
the past half century. In the Connaissance des Tems from 1793 to 1829,
inclusive, it is given, under the authority of the French academicians, at bh.
59m. 53.5s. west of Greenwich.
In England, the useful Requisite Tables make it to be 5h. 59m. 55s.
Don José Joachim de Ferrer, in his valuable list of geographical posi-
tions, published in the Connaissance des Tems for 1817, increases this lon-
gitude to 6A. Om. 24s.
Since that period, this last longitude has superseded the first two above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 authorities ; such as the Connaissance des
Tems from 1830 to 1843, inclusive, and the American Almanac for the same
period. In the absence of the data upon which these various results have been
founded, it would be difficult 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 connexion 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 = 2rn. 45s.
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 6h. Oot. 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 ;