102 METHOD OF COMPILING THE MAP. 
longitude of the Copper Mines, as given on the Mexican boundary map, is 108° 06’; on Major 
Emory’s reconnaissance map it is 108? 12, This position has therefore been moved to the 
east just the amount which Lieut. Whipple moved Albuquerque. Major Emory’s reconnais- 
sance in 1846 has therefore been moved entire between these points 6'to the east, and thus 
reduced to the general map. West of Mount Graham the Gila river has been taken from the 
maps of the surveys under the Boundary Commission. ۱ 
Major Emory’s route in 1846, from the place where he struck the Santa Fé trail to Choteau’s 
island on the Arkansas, is nearly that of the road surveyed by Mr. Brown in 1825-26-21. 
The longitude and latitude of the mouth of Walnut creek and of Choteau’s island, and the 
survey of the river between them, being almost precisely the same. This position of Choteau’s 
island on our map, as obtained from Brown's survey in the manner explained, is about 19’ 
further west than that given by him, and 19’ further west than that given by Major Emory. 
In Major Emory’s report, (page 223,) his determination of longitude of Bent’s Old Fort, by 
seven observation of the distance of Aquile from the moon, is 102° 27’ 19.9", and by four 
observations for the distance of Spica, 103° 26’ 02"; mean of all, 102° 56’ 40". In the list of 
geographical positions given, (page 176 of his report,) this longitude is given 103° 01’, and it 
is so represented on the map. On Captain Frémont's map of routes in 1842— 43-44, the 
longitude of Bent’s Old Fort is given at 103° 45’, and the difference between it and the mouth 
of Fontaine qui Bouit creek, 1? 15’.. This last point, as determined by Captain Frémont in 
1845, is in longitude 104° 42’; subtracting this difference from it, places Bent’s Old Fort in 
longitude 103° 27’, (in the table of positions in his memoir it is given as 103° 33’ 20".) As 
this difference of longitude between the fort and the mouth of the Fontaine qui Bouit creek, 
a distance of about eighty miles, depends upon the topographical reconnaissance with estimated 
distances, it cannot be considered very exact, still its near coincidence to Major Emory's deter- 
mination by the moon's distance from Spica renders its correctness more probable. Taking 
now the map of Captain Gunnison's route up the Arkansas, as prepared by Mr. Egloffstein, 
we find he places Choteau island in 101? 21' being nearly the same as that on the general 
map, (1019 20’,) as obtained from Brown's survey. Captain’ Gunnison's map places the longi- 
tude of Bent’s Old Fort in longitude 103° 24’ 30”; and as the adoption of this saved any change 
in embodying this map, and does not differ materially from my deduction from Capt. Frémont 
and Major Emory's work, I have done so. 
In reducing Major Emory’s reconnoissance from Bent’s Fort to Santa Fé, it would seem that 
as the position of the fort has been moved west, while that of Santa Fé has remained the 
same, the position of the Raton Pass should also be moved to the west. I have, however, 
retained it as given by him: First, because the Spanish peaks, which must have been fixed in 
position by bearings along his route, were placed further east by Captain Gunnison than by 
Major Emory; and, second, because, by taking the position of the crossing of the Canadian as 
fixed by Brown’s survey, and connecting the Pass with it by Lieutenant Abert and Peck’s 
reconnaissance, it would also be necessary to move it to the east. Major Emory’s position for 
the Raton Pass has therefore been retained as being a mean of all the other requirements. 
Lieutenants Peck’s reconnaissance of the Cimarron route, as given on Major Emory’s map, 
makes the position of the “Point of Rocks” somewhat east of that obtained from Brown’s 
survey, which it has been made to conform with. : 
In reducing Lieutenant Abert and Peck's reconnaissance i* the odas in 1845, the trail 
between the Raton Pass and the Cimarron crossing of the Capadian, is made to correspond 
