. Account of an expedition from Pittsburgh to the Rocky Mountains, performed in the years 1819 and '20 : by order of the Hon. Calhoun, sec'y of war: under the command of Major Stephen H. Long. From the notes of Major Long, Mr. T. Say, and other gentlemen of the exploring party. Indians of North America; Discoveries in geography; Indians of North America. , Astronomical and Meteorological Records^ ^c. xxxi Equal altitudes of Sun to find error of Time-piece, (box chrono- meter,J at noon. Sept. 14,1820. Sept. 15, 1820. Time fi'om Noon, A. M. Error of Time- piece. S" 08' 57" 3 07 23
. Account of an expedition from Pittsburgh to the Rocky Mountains, performed in the years 1819 and '20 : by order of the Hon. Calhoun, sec'y of war: under the command of Major Stephen H. Long. From the notes of Major Long, Mr. T. Say, and other gentlemen of the exploring party. Indians of North America; Discoveries in geography; Indians of North America. , Astronomical and Meteorological Records^ ^c. xxxi Equal altitudes of Sun to find error of Time-piece, (box chrono- meter,J at noon. Sept. 14,1820. Sept. 15, 1820. Time fi'om Noon, A. M. Error of Time- piece. S" 08' 57" 3 07 23 3 05 49 3h 14' 23" 3 12 49 3 11 16. 7' 08" slow. Mean time. »3 mean of seven lunar observations, distance of nearest limbs of sun and moon—taken at the moutJi of the Missouri. Sept. 15,1820. Time of observa- tion, P. M. 4*' 20' 25" Baromet. Distance of Sun and Moon. 93° 57' 08" Thermomet. 72° Index error. -f 27' Allowance to be made for error and rate of time-piece, as usual. Longitude deduced, 5'' 59' 48", or 89° 57' W. of Greenwich. The longitude of the mouth of the Missouri as above is 89° 57' W. of Greenwich; and the longitude of St. Louis deduced from a set of lunar observations on the 16th of June, 1819, (see page 10,) is 90° 06' 15" W. of the same meridian. The observations at both places were made with the same instruments, and under equally favourable cir- cumstances, they are accordingly entitled to the same weight as re- spects accuracy. But by a traverse of the river between the two places, a distance of 18 miles, the mouth of the Missouri is found to be only 1' 55" of longitude E. of St. Louis. Now by taking a mean between the two results deduced from observations, and in one case adding, and in the other subtracting 57^ = half the difference of longitude by the traverse, the following results will be obtained, entitled to double the confidence of the result of either of the lunar observations above mentioned indivi
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