PARTIAL RESULTS OF EXPLORATION. 



Heights by the Barometer Continued. 



459 



Memoranda concerning the Meteorological Observations on the Missouri river, by Lieutenant A. J. 



Donclson. 



The barometer used from St. Louis to Fort Pierre was &quot; Green s closed cistern,&quot; No. 718. 

 Its error was assumed to be .050 inch. At Fort Pierre, after a series of readings, it indicated 

 a height of column .050 inch greater than barometer No. 722, which was &quot;Green s open cistern,&quot; 

 of glass. The latter barometer was used from Fort Pierre to Fort Union. It was compared in 

 St. Louis with Dr. Engelmann s standard, and its error was .01 inch. 



In the accompanying tables the barometer has been first reduced to the freezing-point; employ 

 ing for this purpose the tables for barometers with brass scales, then corrected for error, and then 

 for horary variation. For the latter the following scale, kindly furnished by Professor Blodget, 

 and adopted for Fort Union, has been used: 



4 a. m. +0.20 



5 a. m. +0.15 



6 a. m. .000 



7 a. m. .010 



8 a. m. .015 



9 a. m. .025 



10 a. m. .040 



11 a. m. .035 



12 m. -.008 



1 p. m. .000 



2 p. m. +.018 



3 p. m. +.025 



4 p. m. +.030 



5 p. m. +.030 



6 p. m. +.020 



7 p. m. +.010 



8 p. m. +.000 



9 p. m. .015 



10 p. m. .025 



11 p. m. .020 



12 p. m. -.000 



Below Fort Union, the variation at 5 p. m. was taken as +.035. The calculation has been 

 made by using the Smithsonian meteorological tables. 



The numbers in brackets, in the column of heights, denote the estimated height of the instru 

 ment above low water. 



The point of reference was the level of the sea where the height of the barometric column 

 would be 30.000 inches, the temperature being 64. 



A constant number, 34.9, has been added to each calculated height. 



