xxvi Astronomical and Meteorological Records^ ^c. 



edge of the shore, two distances of 400 yards each, in the same right 

 line, and, with a leveling instrument well adjusted and placed at the 

 point from which the distances were measured in opposite directions, 

 found the difference of apparent level between this middle point and 

 the station at the end of the line looking down the river to be 3.5 

 inches. Then turning the instrument round and again adjusting its 

 level, found the difference of apparent level between the middle point 

 and the station at the end of the other line, looking up the river, to be 

 4.75 inches. A mean of the two gives for the difference of apparent 

 level in 400 yards ... - 4.125 inches. 

 Difference of true and apparent level, in do. .411 inches, subtractivc. 



Perpendicular fall of Missouri in 400 yards 3.714 inches. 



The perpendicular fall of the Missouri agreeably to the foregoing 

 estimate is 16.341 inches per mile. 



The difference in the apparent levels, obtained by the two observa- 

 tions as above, may be attributed to the effect of terrestrial refraction, 

 ■which in the first instance would have a tendency to diminish the dif- 

 ference of apparent level, and in the second, to augment it. It was in 

 order to correct this effect of refraction, and also any imperceptible 

 errors in the adjustment of the instrument, that the method was 

 adopted of making two observations, in contrary directions, from a 

 fixed point. The instrument made use of was provided with a spirit 

 level 9 inches in length, and an excellent telescope which magnified 

 about thirty times. 



The observations were made after the spring flood had commenced, 

 and when the surface of the river was thirteen feet above the low- 

 water mark. 



Results of the Observations made at Engineer Cantonment. 

 Rate, of Time-piece, (box chronometer,) between the \7th December, 



1819, and the 7th of January, 

 tildes. 



1819. 

 Dec. 17. 



19. 



5) 



23, 

 24, 



26. 

 1820. 

 Jan. 3. 



5. 



7 



1820, as determined by equal alii- 



Variation of Time- 

 piece for every 12 

 hours. 



Chronometer fast for 

 mean time at noon 

 Do. do. 



Do. do. at midnight 

 Do. slow for mean 

 timeat 10"56'19i" 

 Do. do. at noon 

 Do. do. at midnight 

 Do 



do. at noon 



Do. 

 Do. 

 Do. 



do. 

 do. 

 do. 



do. 

 do. 

 do. 



7' 21" 00'" 



52 

 02 



00 



22 



3 21 00 



4 



5 

 7 



20 



24 



27 



17 

 09 

 42 



41 



08 

 23 



30 

 00 

 14 



39 

 39 

 00 



52" 15"' losins:. 



