COMPUTATION OF ALTITUDES FROM BAROMETRICAL 
OBSERVATIONS —TABLES OF HEIGHTS АХ) DIS- 
TANCES —METEOROLOGICAL REGISTER, 
CHAPTER XVIII. 
COMPUTATION OF ALTITUDES FROM BAROMETRICAL OBSERVATIONS. 
INSTRUMENTS.—READINGS REDUCED TO 32° F.—Loss оғ FIELD-BOOKS ОР 1853.—LIEUTENANT ABBOT'S TABLE OF 
Horary OSCILLATIONS IN THE DES CHUTES VALLEY, OREGON TERRITORY.—MR. DOTY’S OBSERVATIONS FROM FORT 
BENTON TO BADGER RIVER.—CORRESPONDING OBSERVATIONS AT FORT BENTON.—SERGEANT LINT’S OBSERVATIONS 
AT CANTONMENT STEVENS.—ABNORMAL OSCILLATIONS.—COMPUTATION OF ALTITUDES AT THE STATIONS Nos. 19 
AND 20.—GREAT RISE OF THE BAROMETER AT THE BITTER ROOT RIVER.—OBSERVATIONS AT THE MOUTH OF THE 
Sr. REGIS DE BorGIA.—SIMULTANEOUS OBSERVATIONS AT STATIONS 103 AND 114.—MR. DoTY'S OBSERVATIONS 
BETWEEN THE llTH AND 22D OF May, FROM FORT BENTON TO SUN RIVER.—TABLES OF SERGEANT LINT’S OBSER- 
VATIONS FROM FoRT BENTON ACROSS ани AND CLARK’S Pass. 
TABLES OF HEIGHTS AND DISTANCES. 
From Fort BENTON, via TETON AND DEARBORN RIVERS, THROUGH LEWIS AND CLARK'S Pass, SEPTEMBER, 1854.— 
From Fort BENTON, via SUN RIVER AND THE EASTERN BASE OF THE ROCKY MOUNTAINS, TO BIRCH RIVER, May, 
854.—On GOVERNOR STEVENS'S TRIP TO AND FROM THE BLACKFOOT COUNCIL, 1855—56. 
METEOROLOGICAL REGISTER. 
From OCTOBER 2, 1854, ТО NOVEMBER 5, 1855. 
The barometers used on the different expeditions were four of Green’s cistern barometers, 
viz: Numbers 1006, 776, 725, 722, and three of Green’s syphon barometers, viz: Numbers 782, 
769, and 767. The cistern barometer, Number 722, was called a standard barometer, but was 
found, on examination by Mr. Doty, to be out of order, and was accordingly rejected. The 
instrument 1006 was used on the trip to the Blackfoot council. Its index error, as determined 
at Fort Benton by a comparison of it with the two syphon barometers, Numbers 769 and 782, 
was +.025. 
This instrument was the only one whose index error was determined; the others have, there- 
fore, been assumed as correct. 
The instrument used by Mr. Doty in making the observations on his trip to Birch river, and 
by Private Lint, on his trip through Lewis and Clark’s Pass, was instrument Number 776. The 
observations made with the other barometers have been already given in the first volume of 
the Pacific Railroad Explorations. 
In preparing the observations for computation the observed readings were severally reduced 
to what they would have been had the temperature been 32° Fahrenheit, which was done by 
means of the tables of Mr. A. Guyot, published by the Smithsonian Institution. The corrections 
for instrument error were next applied wherever ascertained. 
