The Longitudes given in the subjoined Table are referred to the meridian of Greenwich.

For the determination of astronomical positions, we were provided with the following instruments:

One telescope, magnifying power 120.
One circle, by Gambey, Paris.
One sextant, by Gambey, Paris.
One sextant, by Troughton. One box chronometer, No.7,810, by French.
One Brockbank pocket chronometer.
One small watch with a light chronometer balance, No. 4,632, by Arnold and Dent.

The rate of the chronometer, 7,810, is exhibited in the following statement:

"NEW YORK, May 5, 1842
"Chronometer No. 7,810, by French, is this day at noon--
"Slow of Greenwich mean time, 11' 4"
"Fast of New York mean time, 4h. 45' 1"
"Loses per day 2".7
"ARTHUR STEWART, 74 Merchants' Exchange."

An accident among some rough ground in the neighborhood of the Kansas river, strained the balance of this chronometer, (No. 7,810) and rendered it useless during the remainder of the campaign. From the 9th of June to the 24th of August, inclusively, the longitudes depend upon the Brockbank pocket chronometer; the rate of which, on leaving St. Louis, was fourteen seconds. The rate obtained by observations at Fort Laramie, 14".05, has been used in calculation.

From the 24th of August until the termination of the journey, No. 4,632 (of which the rate was 35".79) was used for the same purposes. The rate of this watch was irregular, and I place little confidence in the few longitudes which depend upon it, though, so far as we have any means of judging, they appear tolerably correct.

Table of Latitudes and Longitudes, deduced from Observations
made during the Journey.

Date

Station

Latitude.

Longitude.

Deg.

min.

sec.

Deg.

min.

sec.

1842

May 27

 St. Louis, residence of Colonel Brunt,

38

37

34

June 8

 Chouteau's lower trading-post; Kansas river,

39

05

57

94

25

46

16

 Left bank of Kansas river. 7 miles above the ford,

39

06

40

95

38

05

18

 Vermilion creek

39

15

19

96

04

07

19

 Cold springs, near the road to Laramie,

39

30

40

96

14

49

20

 Big Blue river,

39

45

08

96

32

35

25

 Little Blue river,

40

26

50

98

22

12

26

 Right bank of Platte river,

40

41

06

98

45

49

27

 Right bank of Platte river.

40

39

32

99

05

24

28

 Right bank of Platte river,

40

39

51

30

 Right bank of Platte river

40

39

55

100

05

47

July 2

 Junction of north and south forks of the Nebraska or Platte river,

41

05

05

100

49

43

4

 South fork of Platte river, left bank,

6

 South fork of Platte river, island

40

51

17

103

07

7

 South fork of Platte river, left bank

40

53

26

103

30

37

11

 South fork of Platte river, St. Vrain's fort ,

40

22

35

105

12

12

12

 Crow creek

40

41

59

104

57

49

13

 On a stream, name unknown

41

08

30

104

39

37

14

 Horse creek. Goshen's hole?

41

40

13

104

24

36

16

 Fort Laramie, near the mouth of Laramie's fork,

42

12

10

104

47

43

23

 North fork of Platte river

42

39

25

104

59

59

24

 North fork of Platte river

42

47

40

25

 North fork of Platte river, Dried Meat camp

42

51

35

105

50

15

26

 North fork of Platte river, noon halt

42

50

08

26

 North fork of Platte river, mouth of Deer creek,

42

52

24

106

08

24

28

 North fork of Platte river, Cache camp,

42

50

53

106

38

26

29

 North fork of Platte river, left bank

42

38

01

106

54

32

30

 North fork of Platte river, Goat island

42

33

27

107

13

29

Aug. 1

 Sweet Water river, one mile below Rock Independence,

42

29

56

107

25

23

4

 Sweet Water river

42

32

31

108

30

13

7

 Sweet Water river

42

27

15

109

21

32

8

 Little Sandy creek, tributary to the Colorado of the West,

42

27

34

109

37

59

9

 New fork, tributary to the Colorado,

42

42

46

109

58

11

10

 Mountain lake,

42

49

49

110

08

03

15

 Highest peak of the Wind River mountains,

19

 Sweet Water, noon halt,

42

24

32

19

 Sweet Water river,

42

22

22

20

 Sweet Water river,

42

31

46

22

 Sweet Water river, noon halt,

42

26

10

22

 Sweet Water river, Rock Independence,

42

29

36

23

 North fork of Platte river, mouth of Sweet Water,

42

27

18

30

 Horse-shoe creek, noon halt,

42

24

24

Sept 3

 North fork of Platte river, right bank,

42

01

40

4

 North fork of Platte river, near Scott's bluffs

41

54

38

5

 North fork of Platte river, right bank, six miles above Chimney rock,

41

43

36

8

 North fork of Platte river, mouth of Ash creek,

41

17

19

9

 North fork of Platte river, right bank

41

14

30

10

 North fork of Platte river, Cedar bluff,

41

10

16

16

 Platte river, noon halt

40

54

31

16

 Platte river, left bank,

40

52

74

17

 Platte river, left bank,

40

42

38

18

 Platte river, left bank,

40

40

21

19

 Platte river, left bank

40

39

44

20

 Platte river, noon halt, left bank,

40

48

19

20

 Platte river, left bank,

40

54

02

21

 Platte river, left bank

41

05

37

23

 Platte river, noon halt, left bank

41

20

20

23

 Platte river, left bank

41

22

52

25

 Platte river, mouth of Loup fork,

41

22

11

28

 Platte river, mouth of Elk Horn river

41

09

34

29

 Platte river, left bank,

41

02

15

Oct. 2

 Bellevue, at the post of the American Fur Company, right bank of the Missouri river

41

08

24

95

20

4

 Left bank of the Missouri, opposite to the right bank of the mouth of the Platte

41

02

11

5

 Missouri river,

40

34

08

6

 Bertholet's island, noon halt,

40

27

08

6

 Missouri river, mouth of Nishnabatona river,

40

16

40

8

 Missouri river, left bank

39

36

02

10

 Missouri river, mouth of the Kansas river

39

06

03