99 [237] 



good condition. Mr. De Smedt, with whom I had passed some days of 

 travel on the Missouri, soon made himself acquainted with the manner 

 of taking observations; and proved it, in furnishing me with a four 

 months' series, made with a care that the most scrupulous examination 

 could only confirm, and embracing the period between the 17th of May 

 and 17th of September, 1839 — an interval during which 1 was exploring 

 the northwest. 



The barometer at St. Louis was situated in a small exposed plain ; that 

 at Camp Kearney was placed in the valley of the Missouri, which is deep, 

 and often three to live miles wide. Using only the noon observations for 

 both, grouping them by 20's, and applying the reduction of the stations to 

 their respective levels, the calculations give the following results : 



Station at Camp Kearney, above St. Louis, by — 

 20 observations at noon, in May and .lune, 1839 

 in June, 1839 

 in June and July, 1839 

 in July and August, 1839 - 

 in August, 1839 

 in September, 1839 - . - 



113 do. do. mean difference of level 



Reduction for St. Louis to the Gulf - 



Altitude of the Missouri, at low water, near Council Bluffs, 

 above Gulf of Mexico . . - - - 



These detailed results appear to me satisfactory enough, regard being had 

 to the horizontal distance between the two stations. 



2. Having made, in 1836 and 1837, a long stay at St. Peter's, under the 

 hospitable roof of my particular friend Major Taliaferro, (then and now the 

 Indian agent,) and having again visited the place in 1838 and 1839,1 have 

 had the occasion of determining its altitude with barometers of dissim- 

 ilar construction, and by observations made in the course of three different 

 years. 



The barometer was placed in my chamber at the Indian agency near 

 Fort Snelling, on the beautifol plateau of St. Peter's, which presents a per- 

 fectly open plain. 



The following are the results of the calculation, reduced to the level of 

 the Mississippi, for both stations respectively : 



Station at St. Peter's, above St. Louis : 



1836, July. — By 20 observations at noon, referred to the ba- ^ 



rometer at the University of St. Louis, (these observations 

 were made before my departure for the sources of the Mis- 

 sissippi) ...-.-. 342 feet. 



October, — By 20 observations at noon, referred to the barome- 

 ter of the University of St. Louis, (these observations were 

 made on my return from the sources of the Mississippi) - 381 " 



1838, May and June. — By 20 observations at noon, referred 



to Dr. Bngelmann's barometer at St. l^ouis - - 365 " 



1839, September. — By 20 observations at noon, referred, inter- 

 mediately through another barometer, to Dr. Engelmann's 359 " 



