PART 11. 



Containing the Calculations of Observations made by Major Long and 

 Lieutenant Swift, on a tour from the Council Bluffs on the Missouri 

 river, ivestward along the river Flatte to its head waters in the 

 Rocky Mountains, — thence southwardly to the head waters of the 

 Jirkansa and Canadian rivers, — and down said rivers to Belle 

 Point, performed in 1820, under the command of Major S. H. Long, 

 of the United States' Topographical Engineers. 



JSTote. — The instruments used in making the following astronomi- 

 cal observations, were a portable sextant of 5 inches radius, graduated 

 by the assistance of the vernier to 30", made by Gary, London, ac- 

 companied by a mercurial artificial horizon with a glass frame, and 

 an excellent patent-lever watch, by Robert Roskell. 



Camp on the river Platte, at the fording place of the Pawnee Indians, 

 twenty-seven miles below the confluence of the JYorth and South, or 

 Padouca Forks. 



June 20, 1820. 



Meridian altitude of sun's 



lower limb 

 Extent of horizon, (a level 



sheet of water) 

 Height of observer's eye above 



horizon - - - 



Index error — 4' 15". Latitude ^ 

 deduced - - - S 



72° 23' 

 700 yards. 

 31 feet. 



40° 59'15"N. 



Equal altitudes of Sun to find error of Watch. 



Error of Watch. 



June 20, 1820. 



Time from Noon, 

 A. M. 



2'' 32' 26" 

 2 29 36 



Time from Noon, 

 P. M 



2" 32' 34" 

 2 29 46 



1' 15" fast. 

 Mean time. 



Camp on the Platte, thirty-two miles below the point where it issues 

 from the Rocky Mountains. 



July 4, 1820. 



Meridian double altitude of ] 

 star Antaris, («. Scorpii) ' 



Index error — 3' 45". Latitude 

 deduced . - - 



48° 10' 00' 



39° 57' 40" N. 



