METHOD OF COMPILING THE MAP. 101 
Marcy east to the amount of 20’. This, again, is the only way of making his survey of 
the North Fork agree with the position determined for it by Lieutenant Abert’s survey in 1845, 
as will be explained further on. 
I have therefore moved the sources of Red river 20’ east of Captain Marcy’s position, the 
mouth of the Little Witchita 30’ to the east, and, in order to subject his map to the least dis- 
tortion which the changes require, the camp at Otter Tail creek 25’ to the east, placing it in 
longitude 99° 35. By moving this point with the other parts of the map, I have been enabled 
to represent the routes of this expedition in nearly the same relative positions as on the original 
map. The errors I have supposed, for the purpose of representing this information, are within 
the limits of error of determination of longitude by the means employed. 
On Captain Marcy’s map of the sources of the Brazos and Big Witchita, made in 1854, Fort 
Belknap is placed in longitude 98° 47’; the mouth of Panther creek 100°; Large spring, near 
the Big Wachita, 98° 48’; on the general map these same points are, respectively, 98° 36’, 
99° 50’, 99° 35’. These are the only points I can recognize to be nearly common; although 
the last two are not certain, they go to show that the whole of the positions on the map are 
from 10’ to 12’ too far west, and that the different parts are relatively correct. As reduced on 
our map, the routes appear about 11 east of the geographical positions given on the original. 
The survey of the southern boundary of Kansas, by Lieut. Col. J. E. Johnston, in 1857, has 
been adopted on our map without any change, as it was made by means superior to those pos- 
sessed by any other surveyor or explorer whose lines are crossed by his. 
The survey of the road from Old Fort Osage, through to San Fernando de Taos, in 1825, 1826, 
and 1827, by J. C. Brown, C. E., has also been adopted as given by him with, the following 
modifications: This survey was made with chain and compass, corrected by astronomical 
observations, with a sextant for latitude. The longitudes were fixed by assuming, from the 
previous determinations of others, that Old Fort Osage was in longitude 93° 51’. According 
to the position I have assigned Fort Osage, it is in longitnde 94° 14’, requiring an addition of 
23’ of longitude to all points of the survey. The point on this route where the southern 
seedy of Kansas strikes the Cimarron, is determined on our map, by Colonel Johnston’s 
urvey, to bei in longitude 102° 10’. On Brown's map it is in longitude 101° 52’; showing that 
bi is work at ‘this point requires to be moved 18’ west. Brown’s survey between this point and 
Fort Osage is consequently adapted to the general map by shortening it 5! in longitude. 
West of this point, on the Cimarron, Brown’s map is nearly copied, all points being moved 18 
westward. Taos thus comes to be located i in longitude 105° 30’, which is nearly 10’ east of its 
position on Major Emory’s map. 
Major Emory’s determination of the longitude of Santa Fé (106° 04’ by lunar distances, see 
page 266 of his report of Mil. Recon.) is given on his map at 106° 02’. The Land Office con- 
nexions with the Mexican boundary survey and Lieut. Whipple’s determinations of Albuquerque 
agree; and applying this same connexion to Sant Fé, its longitude would be about 106° 02’, 
agreeing with Major Emory’s map. This longitude has been adopted. The position of Albu- 
querque and Isletta having been moved 6’ to the east-of Major Emory’s position, the portion of 
his map between these points and Santa Fé was shortened in longitude to this amount. The 
* In the summer following the date of this Memoir, the observations for the determination of the position of the 100th 
meridian have shown even a greater error in regard to Marcy's longitude of the mouth of Otter creek. 
